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	$35.42	5.845%	$37.4903	$37.49	$37.50	$37.50
Purchase #2	$116.83	13.202%	$132.2539	$132.25	$132.25	$132.30
Purchase #3	$158.96	4.218%	$165.6649	$165.66	$165.65	$165.70
Purchase #4	$107.83	10.107%	$118.7284	$118.73	$118.75	$118.70
Purchase #5	$57.53	9.231%	$62.8406	$62.84	$62.85	$62.80
Purchase #6	$223.54	5.857%	$236.6327	$236.63	$236.65	$236.60
Purchase #7	$151.33	5.414%	$159.523	$159.52	$159.50	$159.50
7 purchase totals =	$851.44		$913.1338	$913.12	$913.15	$913.10