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	$201.28	6.166%	$213.6909	$213.69	$213.70	$213.70
Purchase #2	$91.58	6.477%	$97.5116	$97.51	$97.50	$97.50
Purchase #3	$61.66	13.813%	$70.1771	$70.18	$70.20	$70.20
Purchase #4	$190.27	3.352%	$196.6479	$196.65	$196.65	$196.60
Purchase #5	$106.28	5.482%	$112.1063	$112.11	$112.10	$112.10
Purchase #6	$200.78	10.482%	$221.8258	$221.83	$221.85	$221.80
Purchase #7	$114.82	10.476%	$126.8485	$126.85	$126.85	$126.80
7 purchase totals =	$966.67		$1,038.8081	$1,038.82	$1,038.85	$1,038.70