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	$59.72	10.329%	$65.8885	$65.89	$65.90	$65.90
Purchase #2	$214.69	3.659%	$222.5455	$222.55	$222.55	$222.50
Purchase #3	$46.29	4.107%	$48.1911	$48.19	$48.20	$48.20
Purchase #4	$94.64	6.627%	$100.9118	$100.91	$100.90	$100.90
Purchase #5	$144.97	7.133%	$155.3107	$155.31	$155.30	$155.30
Purchase #6	$71.43	10.862%	$79.1887	$79.19	$79.20	$79.20
Purchase #7	$215.85	4.320%	$225.1747	$225.17	$225.15	$225.20
7 purchase totals =	$847.59		$897.2110	$897.21	$897.20	$897.20