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	$23.58	6.560%	$25.1268	$25.13	$25.15	$25.10
Purchase #2	$196.50	4.872%	$206.0735	$206.07	$206.05	$206.10
Purchase #3	$79.95	11.480%	$89.1283	$89.13	$89.15	$89.10
Purchase #4	$38.81	10.660%	$42.9471	$42.95	$42.95	$42.90
Purchase #5	$19.52	6.578%	$20.804	$20.80	$20.80	$20.80
Purchase #6	$208.68	7.317%	$223.9491	$223.95	$223.95	$223.90
Purchase #7	$82.97	6.504%	$88.3664	$88.37	$88.35	$88.40
7 purchase totals =	$650.01		$696.3952	$696.40	$696.40	$696.30