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	$228.33	13.578%	$259.3326	$259.33	$259.35	$259.30
Purchase #2	$184.32	6.482%	$196.2676	$196.27	$196.25	$196.30
Purchase #3	$66.78	6.537%	$71.1454	$71.15	$71.15	$71.10
Purchase #4	$213.30	9.833%	$234.2738	$234.27	$234.25	$234.30
Purchase #5	$203.89	5.311%	$214.7186	$214.72	$214.70	$214.70
Purchase #6	$105.63	4.769%	$110.6675	$110.67	$110.65	$110.70
Purchase #7	$33.95	10.841%	$37.6305	$37.63	$37.65	$37.60
7 purchase totals =	$1,036.20		$1,124.0360	$1,124.04	$1,124.00	$1,124.00