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	$240.72	3.258%	$248.5627	$248.56	$248.55	$248.60
Purchase #2	$184.34	13.769%	$209.7218	$209.72	$209.70	$209.70
Purchase #3	$92.57	4.543%	$96.7755	$96.78	$96.80	$96.80
Purchase #4	$27.90	13.229%	$31.5909	$31.59	$31.60	$31.60
Purchase #5	$151.44	12.294%	$170.058	$170.06	$170.05	$170.10
Purchase #6	$242.66	9.296%	$265.2177	$265.22	$265.20	$265.20
Purchase #7	$137.40	5.272%	$144.6437	$144.64	$144.65	$144.60
7 purchase totals =	$1,077.03		$1,166.5703	$1,166.57	$1,166.55	$1,166.60