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	$134.59	9.766%	$147.7341	$147.73	$147.75	$147.70
Purchase #2	$108.87	7.318%	$116.8371	$116.84	$116.85	$116.80
Purchase #3	$114.58	13.444%	$129.9841	$129.98	$130.00	$130.00
Purchase #4	$226.80	3.536%	$234.8196	$234.82	$234.80	$234.80
Purchase #5	$97.33	3.606%	$100.8397	$100.84	$100.85	$100.80
Purchase #6	$219.52	9.746%	$240.9144	$240.91	$240.90	$240.90
Purchase #7	$174.70	12.607%	$196.7244	$196.72	$196.70	$196.70
7 purchase totals =	$1,076.39		$1,167.8534	$1,167.84	$1,167.85	$1,167.70