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	$183.42	7.102%	$196.4465	$196.45	$196.45	$196.40
Purchase #2	$97.45	8.658%	$105.8872	$105.89	$105.90	$105.90
Purchase #3	$111.32	10.369%	$122.8628	$122.86	$122.85	$122.90
Purchase #4	$86.36	6.571%	$92.0347	$92.03	$92.05	$92.00
Purchase #5	$16.29	9.265%	$17.7993	$17.80	$17.80	$17.80
Purchase #6	$20.28	3.184%	$20.9257	$20.93	$20.95	$20.90
Purchase #7	$144.48	3.194%	$149.0947	$149.09	$149.10	$149.10
7 purchase totals =	$659.60		$705.0509	$705.05	$705.10	$705.00