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	$210.27	3.260%	$217.1248	$217.12	$217.10	$217.10
Purchase #2	$32.54	7.185%	$34.878	$34.88	$34.90	$34.90
Purchase #3	$22.45	8.173%	$24.2848	$24.28	$24.30	$24.30
Purchase #4	$53.88	9.460%	$58.977	$58.98	$59.00	$59.00
Purchase #5	$58.89	6.849%	$62.9234	$62.92	$62.90	$62.90
Purchase #6	$200.71	11.397%	$223.5849	$223.58	$223.60	$223.60
Purchase #7	$151.87	5.872%	$160.7878	$160.79	$160.80	$160.80
7 purchase totals =	$730.61		$782.5607	$782.55	$782.60	$782.60