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	$93.84	5.782%	$99.2658	$99.27	$99.25	$99.30
Purchase #2	$75.52	12.539%	$84.9895	$84.99	$85.00	$85.00
Purchase #3	$100.81	10.838%	$111.7358	$111.74	$111.75	$111.70
Purchase #4	$203.47	9.300%	$222.3927	$222.39	$222.40	$222.40
Purchase #5	$163.88	7.300%	$175.8432	$175.84	$175.85	$175.80
Purchase #6	$149.95	12.123%	$168.1284	$168.13	$168.15	$168.10
Purchase #7	$105.58	7.648%	$113.6548	$113.65	$113.65	$113.70
7 purchase totals =	$893.05		$976.0102	$976.01	$976.05	$976.00