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	$41.95	10.809%	$46.4844	$46.48	$46.50	$46.50
Purchase #2	$182.38	5.369%	$192.172	$192.17	$192.15	$192.20
Purchase #3	$8.73	5.769%	$9.2336	$9.23	$9.25	$9.20
Purchase #4	$172.25	4.339%	$179.7239	$179.72	$179.70	$179.70
Purchase #5	$200.59	11.590%	$223.8384	$223.84	$223.85	$223.80
Purchase #6	$119.57	12.814%	$134.8917	$134.89	$134.90	$134.90
Purchase #7	$172.93	7.308%	$185.5677	$185.57	$185.55	$185.60
7 purchase totals =	$898.40		$971.9117	$971.90	$971.90	$971.90