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	$93.35	10.537%	$103.1863	$103.19	$103.20	$103.20
Purchase #2	$11.93	12.333%	$13.4013	$13.40	$13.40	$13.40
Purchase #3	$73.41	6.772%	$78.3813	$78.38	$78.40	$78.40
Purchase #4	$229.84	10.638%	$254.2904	$254.29	$254.30	$254.30
Purchase #5	$59.59	13.210%	$67.4618	$67.46	$67.45	$67.50
Purchase #6	$151.96	4.628%	$158.9927	$158.99	$159.00	$159.00
Purchase #7	$83.84	12.833%	$94.5992	$94.60	$94.60	$94.60
7 purchase totals =	$703.92		$770.3130	$770.31	$770.35	$770.40