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	$221.31	7.145%	$237.1226	$237.12	$237.10	$237.10
Purchase #2	$63.90	12.457%	$71.86	$71.86	$71.85	$71.90
Purchase #3	$179.90	10.155%	$198.1688	$198.17	$198.15	$198.20
Purchase #4	$234.28	11.533%	$261.2995	$261.30	$261.30	$261.30
Purchase #5	$241.38	10.102%	$265.7642	$265.76	$265.75	$265.80
Purchase #6	$36.25	7.132%	$38.8354	$38.84	$38.85	$38.80
Purchase #7	$72.71	7.693%	$78.3036	$78.30	$78.30	$78.30
7 purchase totals =	$1,049.73		$1,151.3541	$1,151.35	$1,151.30	$1,151.40