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	$168.67	7.392%	$181.1381	$181.14	$181.15	$181.10
Purchase #2	$114.59	13.646%	$130.227	$130.23	$130.25	$130.20
Purchase #3	$141.81	5.620%	$149.7797	$149.78	$149.80	$149.80
Purchase #4	$71.88	9.169%	$78.4707	$78.47	$78.45	$78.50
Purchase #5	$151.25	9.696%	$165.9152	$165.92	$165.90	$165.90
Purchase #6	$109.55	7.224%	$117.4639	$117.46	$117.45	$117.50
Purchase #7	$27.58	3.836%	$28.638	$28.64	$28.65	$28.60
7 purchase totals =	$785.33		$851.6326	$851.64	$851.65	$851.60