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	$150.35	10.215%	$165.7083	$165.71	$165.70	$165.70
Purchase #2	$82.61	7.167%	$88.5307	$88.53	$88.55	$88.50
Purchase #3	$145.78	6.422%	$155.142	$155.14	$155.15	$155.10
Purchase #4	$70.86	10.387%	$78.2202	$78.22	$78.20	$78.20
Purchase #5	$245.37	10.231%	$270.4738	$270.47	$270.45	$270.50
Purchase #6	$12.64	7.160%	$13.545	$13.55	$13.55	$13.50
Purchase #7	$69.30	3.582%	$71.7823	$71.78	$71.80	$71.80
7 purchase totals =	$776.91		$843.4023	$843.40	$843.40	$843.30