Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$93.29	11.403%	$103.9279	$103.93	$103.95	$103.90
Purchase #2	$162.94	13.296%	$184.6045	$184.60	$184.60	$184.60
Purchase #3	$248.27	13.242%	$281.1459	$281.15	$281.15	$281.10
Purchase #4	$135.53	13.740%	$154.1518	$154.15	$154.15	$154.20
Purchase #5	$130.48	10.560%	$144.2587	$144.26	$144.25	$144.30
Purchase #6	$147.25	3.416%	$152.2801	$152.28	$152.30	$152.30
Purchase #7	$234.90	12.642%	$264.5961	$264.60	$264.60	$264.60
7 purchase totals =	$1,152.66		$1,284.9650	$1,284.97	$1,285.00	$1,285.00