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	$88.47	12.735%	$99.7367	$99.74	$99.75	$99.70
Purchase #2	$34.56	6.849%	$36.927	$36.93	$36.95	$36.90
Purchase #3	$58.76	10.183%	$64.7435	$64.74	$64.75	$64.70
Purchase #4	$28.62	12.351%	$32.1549	$32.15	$32.15	$32.20
Purchase #5	$77.62	5.223%	$81.6741	$81.67	$81.65	$81.70
Purchase #6	$100.73	10.489%	$111.2956	$111.30	$111.30	$111.30
Purchase #7	$66.65	7.320%	$71.5288	$71.53	$71.55	$71.50
7 purchase totals =	$455.41		$498.0606	$498.06	$498.10	$498.00