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	$9.66	4.137%	$10.0596	$10.06	$10.05	$10.10
Purchase #2	$70.51	6.681%	$75.2208	$75.22	$75.20	$75.20
Purchase #3	$157.32	7.755%	$169.5202	$169.52	$169.50	$169.50
Purchase #4	$221.80	5.454%	$233.897	$233.90	$233.90	$233.90
Purchase #5	$111.77	10.869%	$123.9183	$123.92	$123.90	$123.90
Purchase #6	$194.75	13.564%	$221.1659	$221.17	$221.15	$221.20
Purchase #7	$80.55	10.680%	$89.1527	$89.15	$89.15	$89.20
7 purchase totals =	$846.36		$922.9345	$922.94	$922.85	$923.00