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	$179.64	5.109%	$188.8178	$188.82	$188.80	$188.80
Purchase #2	$165.27	8.824%	$179.8534	$179.85	$179.85	$179.90
Purchase #3	$97.62	13.755%	$111.0476	$111.05	$111.05	$111.00
Purchase #4	$227.45	5.312%	$239.5321	$239.53	$239.55	$239.50
Purchase #5	$80.61	10.140%	$88.7839	$88.78	$88.80	$88.80
Purchase #6	$176.52	13.571%	$200.4755	$200.48	$200.50	$200.50
Purchase #7	$92.37	4.480%	$96.5082	$96.51	$96.50	$96.50
7 purchase totals =	$1,019.48		$1,105.0185	$1,105.02	$1,105.05	$1,105.00