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	$144.52	4.817%	$151.4815	$151.48	$151.50	$151.50
Purchase #2	$163.90	12.512%	$184.4072	$184.41	$184.40	$184.40
Purchase #3	$88.70	4.498%	$92.6897	$92.69	$92.70	$92.70
Purchase #4	$235.32	12.399%	$264.4973	$264.50	$264.50	$264.50
Purchase #5	$21.84	7.441%	$23.4651	$23.47	$23.45	$23.50
Purchase #6	$130.71	4.286%	$136.3122	$136.31	$136.30	$136.30
Purchase #7	$89.26	11.105%	$99.1723	$99.17	$99.15	$99.20
7 purchase totals =	$874.25		$952.0253	$952.03	$952.00	$952.10