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	$110.95	7.246%	$118.9894	$118.99	$119.00	$119.00
Purchase #2	$147.49	4.832%	$154.6167	$154.62	$154.60	$154.60
Purchase #3	$163.74	5.330%	$172.4673	$172.47	$172.45	$172.50
Purchase #4	$105.34	12.465%	$118.4706	$118.47	$118.45	$118.50
Purchase #5	$62.33	8.663%	$67.7296	$67.73	$67.75	$67.70
Purchase #6	$85.91	4.427%	$89.7132	$89.71	$89.70	$89.70
Purchase #7	$94.70	10.275%	$104.4304	$104.43	$104.45	$104.40
7 purchase totals =	$770.46		$826.4172	$826.42	$826.40	$826.40