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	$57.54	3.627%	$59.627	$59.63	$59.65	$59.60
Purchase #2	$90.99	5.142%	$95.6687	$95.67	$95.65	$95.70
Purchase #3	$11.36	13.736%	$12.9204	$12.92	$12.90	$12.90
Purchase #4	$40.60	8.331%	$43.9824	$43.98	$44.00	$44.00
Purchase #5	$55.30	6.763%	$59.0399	$59.04	$59.05	$59.00
Purchase #6	$25.76	9.505%	$28.2085	$28.21	$28.20	$28.20
Purchase #7	$200.32	4.762%	$209.8592	$209.86	$209.85	$209.90
7 purchase totals =	$481.87		$509.3061	$509.31	$509.30	$509.30