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	$240.90	7.867%	$259.8516	$259.85	$259.85	$259.90
Purchase #2	$64.74	12.604%	$72.8998	$72.90	$72.90	$72.90
Purchase #3	$169.97	10.681%	$188.1245	$188.12	$188.10	$188.10
Purchase #4	$82.38	11.441%	$91.8051	$91.81	$91.80	$91.80
Purchase #5	$185.38	13.144%	$209.7463	$209.75	$209.75	$209.70
Purchase #6	$214.37	10.124%	$236.0728	$236.07	$236.05	$236.10
Purchase #7	$116.78	10.152%	$128.6355	$128.64	$128.65	$128.60
7 purchase totals =	$1,074.52		$1,187.1356	$1,187.14	$1,187.10	$1,187.10