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	$209.59	4.272%	$218.5437	$218.54	$218.55	$218.50
Purchase #2	$45.68	5.236%	$48.0718	$48.07	$48.05	$48.10
Purchase #3	$196.51	7.838%	$211.9125	$211.91	$211.90	$211.90
Purchase #4	$152.33	13.647%	$173.1185	$173.12	$173.10	$173.10
Purchase #5	$213.51	13.848%	$243.0769	$243.08	$243.10	$243.10
Purchase #6	$52.43	6.712%	$55.9491	$55.95	$55.95	$55.90
Purchase #7	$157.61	9.449%	$172.5026	$172.50	$172.50	$172.50
7 purchase totals =	$1,027.66		$1,123.1751	$1,123.17	$1,123.15	$1,123.10