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	$64.52	11.550%	$71.9721	$71.97	$71.95	$72.00
Purchase #2	$55.43	13.236%	$62.7667	$62.77	$62.75	$62.80
Purchase #3	$207.49	11.368%	$231.0775	$231.08	$231.10	$231.10
Purchase #4	$93.85	12.454%	$105.5381	$105.54	$105.55	$105.50
Purchase #5	$126.80	7.848%	$136.7513	$136.75	$136.75	$136.80
Purchase #6	$171.40	10.204%	$188.8897	$188.89	$188.90	$188.90
Purchase #7	$209.98	6.529%	$223.6896	$223.69	$223.70	$223.70
7 purchase totals =	$929.47		$1,020.6850	$1,020.69	$1,020.70	$1,020.80