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	$56.92	8.223%	$61.6005	$61.60	$61.60	$61.60
Purchase #2	$115.82	3.845%	$120.2733	$120.27	$120.25	$120.30
Purchase #3	$114.50	9.156%	$124.9836	$124.98	$125.00	$125.00
Purchase #4	$220.61	10.558%	$243.902	$243.90	$243.90	$243.90
Purchase #5	$176.80	7.766%	$190.5303	$190.53	$190.55	$190.50
Purchase #6	$28.72	11.717%	$32.0851	$32.09	$32.10	$32.10
Purchase #7	$119.53	7.158%	$128.086	$128.09	$128.10	$128.10
7 purchase totals =	$832.90		$901.4608	$901.46	$901.50	$901.50