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	$11.45	3.170%	$11.813	$11.81	$11.80	$11.80
Purchase #2	$60.57	11.526%	$67.5513	$67.55	$67.55	$67.60
Purchase #3	$28.44	13.735%	$32.3462	$32.35	$32.35	$32.30
Purchase #4	$43.38	5.176%	$45.6253	$45.63	$45.65	$45.60
Purchase #5	$139.31	8.523%	$151.1834	$151.18	$151.20	$151.20
Purchase #6	$216.59	3.122%	$223.3519	$223.35	$223.35	$223.40
Purchase #7	$234.65	7.469%	$252.176	$252.18	$252.20	$252.20
7 purchase totals =	$734.39		$784.0471	$784.05	$784.10	$784.10