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	$190.78	5.319%	$200.9276	$200.93	$200.95	$200.90
Purchase #2	$36.74	13.568%	$41.7249	$41.72	$41.70	$41.70
Purchase #3	$63.67	13.359%	$72.1757	$72.18	$72.20	$72.20
Purchase #4	$238.38	3.823%	$247.4933	$247.49	$247.50	$247.50
Purchase #5	$197.72	6.142%	$209.864	$209.86	$209.85	$209.90
Purchase #6	$216.66	13.728%	$246.4031	$246.40	$246.40	$246.40
Purchase #7	$69.53	3.530%	$71.9844	$71.98	$72.00	$72.00
7 purchase totals =	$1,013.48		$1,090.5730	$1,090.56	$1,090.60	$1,090.60