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	$5.29	4.449%	$5.5254	$5.53	$5.55	$5.50
Purchase #2	$56.67	8.670%	$61.5833	$61.58	$61.60	$61.60
Purchase #3	$247.99	5.804%	$262.3833	$262.38	$262.40	$262.40
Purchase #4	$203.77	9.418%	$222.9611	$222.96	$222.95	$223.00
Purchase #5	$37.42	10.837%	$41.4752	$41.48	$41.50	$41.50
Purchase #6	$174.46	7.692%	$187.8795	$187.88	$187.90	$187.90
Purchase #7	$170.71	12.173%	$191.4905	$191.49	$191.50	$191.50
7 purchase totals =	$896.31		$973.2983	$973.30	$973.40	$973.40