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	$158.63	6.843%	$169.4851	$169.49	$169.50	$169.50
Purchase #2	$99.70	7.762%	$107.4387	$107.44	$107.45	$107.40
Purchase #3	$199.72	7.727%	$215.1524	$215.15	$215.15	$215.20
Purchase #4	$182.78	7.413%	$196.3295	$196.33	$196.35	$196.30
Purchase #5	$211.70	13.432%	$240.1355	$240.14	$240.15	$240.10
Purchase #6	$69.72	12.666%	$78.5507	$78.55	$78.55	$78.60
Purchase #7	$159.34	3.820%	$165.4268	$165.43	$165.45	$165.40
7 purchase totals =	$1,081.59		$1,172.5187	$1,172.53	$1,172.60	$1,172.50