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	$125.25	7.680%	$134.8692	$134.87	$134.85	$134.90
Purchase #2	$31.79	5.343%	$33.4885	$33.49	$33.50	$33.50
Purchase #3	$155.70	11.378%	$173.4155	$173.42	$173.40	$173.40
Purchase #4	$67.53	6.432%	$71.8735	$71.87	$71.85	$71.90
Purchase #5	$91.58	6.561%	$97.5886	$97.59	$97.60	$97.60
Purchase #6	$59.95	7.561%	$64.4828	$64.48	$64.50	$64.50
Purchase #7	$135.98	6.665%	$145.0431	$145.04	$145.05	$145.00
7 purchase totals =	$667.78		$720.7612	$720.76	$720.75	$720.80