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	$91.98	8.229%	$99.549	$99.55	$99.55	$99.50
Purchase #2	$40.66	9.799%	$44.6443	$44.64	$44.65	$44.60
Purchase #3	$150.41	6.591%	$160.3235	$160.32	$160.30	$160.30
Purchase #4	$244.62	12.640%	$275.54	$275.54	$275.55	$275.50
Purchase #5	$52.90	13.403%	$59.9902	$59.99	$60.00	$60.00
Purchase #6	$52.46	3.485%	$54.2882	$54.29	$54.30	$54.30
Purchase #7	$118.40	6.844%	$126.5033	$126.50	$126.50	$126.50
7 purchase totals =	$751.43		$820.8385	$820.83	$820.85	$820.70