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	$222.90	9.518%	$244.1156	$244.12	$244.10	$244.10
Purchase #2	$168.26	3.362%	$173.9169	$173.92	$173.90	$173.90
Purchase #3	$60.54	12.557%	$68.142	$68.14	$68.15	$68.10
Purchase #4	$168.81	11.738%	$188.6249	$188.62	$188.60	$188.60
Purchase #5	$70.55	11.422%	$78.6082	$78.61	$78.60	$78.60
Purchase #6	$232.50	4.577%	$243.1415	$243.14	$243.15	$243.10
Purchase #7	$246.98	12.822%	$278.6478	$278.65	$278.65	$278.60
7 purchase totals =	$1,170.54		$1,275.1969	$1,275.20	$1,275.15	$1,275.00