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	$71.69	9.419%	$78.4425	$78.44	$78.45	$78.40
Purchase #2	$169.67	13.428%	$192.4533	$192.45	$192.45	$192.50
Purchase #3	$241.96	12.795%	$272.9188	$272.92	$272.90	$272.90
Purchase #4	$40.53	3.780%	$42.062	$42.06	$42.05	$42.10
Purchase #5	$64.65	8.434%	$70.1026	$70.10	$70.10	$70.10
Purchase #6	$247.29	6.813%	$264.1379	$264.14	$264.15	$264.10
Purchase #7	$216.52	8.448%	$234.8116	$234.81	$234.80	$234.80
7 purchase totals =	$1,052.31		$1,154.9287	$1,154.92	$1,154.90	$1,154.90