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	$197.71	10.658%	$218.7819	$218.78	$218.80	$218.80
Purchase #2	$219.84	10.724%	$243.4156	$243.42	$243.40	$243.40
Purchase #3	$89.45	11.340%	$99.5936	$99.59	$99.60	$99.60
Purchase #4	$95.70	13.383%	$108.5075	$108.51	$108.50	$108.50
Purchase #5	$110.88	11.144%	$123.2365	$123.24	$123.25	$123.20
Purchase #6	$148.91	7.137%	$159.5377	$159.54	$159.55	$159.50
Purchase #7	$11.66	10.560%	$12.8913	$12.89	$12.90	$12.90
7 purchase totals =	$874.15		$965.9641	$965.97	$966.00	$965.90