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	$107.57	7.204%	$115.3193	$115.32	$115.30	$115.30
Purchase #2	$95.87	3.638%	$99.3578	$99.36	$99.35	$99.40
Purchase #3	$32.37	4.208%	$33.7321	$33.73	$33.75	$33.70
Purchase #4	$65.90	9.170%	$71.943	$71.94	$71.95	$71.90
Purchase #5	$195.87	13.801%	$222.902	$222.90	$222.90	$222.90
Purchase #6	$9.62	4.304%	$10.034	$10.03	$10.05	$10.00
Purchase #7	$182.31	9.519%	$199.6641	$199.66	$199.65	$199.70
7 purchase totals =	$689.51		$752.9523	$752.94	$752.95	$752.90