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	$177.27	10.855%	$196.5127	$196.51	$196.50	$196.50
Purchase #2	$69.84	5.397%	$73.6093	$73.61	$73.60	$73.60
Purchase #3	$52.99	9.315%	$57.926	$57.93	$57.95	$57.90
Purchase #4	$48.60	9.541%	$53.2369	$53.24	$53.25	$53.20
Purchase #5	$173.62	4.846%	$182.0336	$182.03	$182.05	$182.00
Purchase #6	$35.98	13.436%	$40.8143	$40.81	$40.80	$40.80
Purchase #7	$63.67	5.479%	$67.1585	$67.16	$67.15	$67.20
7 purchase totals =	$621.97		$671.2913	$671.29	$671.30	$671.20