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	$187.69	12.325%	$210.8228	$210.82	$210.80	$210.80
Purchase #2	$172.62	13.155%	$195.3282	$195.33	$195.35	$195.30
Purchase #3	$77.27	3.262%	$79.7905	$79.79	$79.80	$79.80
Purchase #4	$133.78	6.224%	$142.1065	$142.11	$142.10	$142.10
Purchase #5	$239.82	7.601%	$258.0487	$258.05	$258.05	$258.00
Purchase #6	$88.50	13.755%	$100.6732	$100.67	$100.65	$100.70
Purchase #7	$59.30	13.471%	$67.2883	$67.29	$67.30	$67.30
7 purchase totals =	$958.98		$1,054.0582	$1,054.06	$1,054.05	$1,054.00