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	$187.99	4.539%	$196.5229	$196.52	$196.50	$196.50
Purchase #2	$154.86	13.598%	$175.9179	$175.92	$175.90	$175.90
Purchase #3	$50.70	7.630%	$54.5684	$54.57	$54.55	$54.60
Purchase #4	$246.83	9.318%	$269.8296	$269.83	$269.85	$269.80
Purchase #5	$93.53	3.418%	$96.7269	$96.73	$96.75	$96.70
Purchase #6	$208.25	7.339%	$223.5335	$223.53	$223.55	$223.50
Purchase #7	$89.38	12.570%	$100.6151	$100.62	$100.60	$100.60
7 purchase totals =	$1,031.54		$1,117.7143	$1,117.72	$1,117.70	$1,117.60