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	$195.82	4.455%	$204.5438	$204.54	$204.55	$204.50
Purchase #2	$161.75	11.528%	$180.3965	$180.40	$180.40	$180.40
Purchase #3	$168.64	10.109%	$185.6878	$185.69	$185.70	$185.70
Purchase #4	$40.30	4.218%	$41.9999	$42.00	$42.00	$42.00
Purchase #5	$46.46	4.366%	$48.4884	$48.49	$48.50	$48.50
Purchase #6	$140.58	13.193%	$159.1267	$159.13	$159.15	$159.10
Purchase #7	$197.97	10.384%	$218.5272	$218.53	$218.55	$218.50
7 purchase totals =	$951.52		$1,038.7703	$1,038.78	$1,038.85	$1,038.70