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	$55.59	10.705%	$61.5409	$61.54	$61.55	$61.50
Purchase #2	$212.42	7.362%	$228.0584	$228.06	$228.05	$228.10
Purchase #3	$54.57	8.485%	$59.2003	$59.20	$59.20	$59.20
Purchase #4	$116.53	7.432%	$125.1905	$125.19	$125.20	$125.20
Purchase #5	$232.44	11.220%	$258.5198	$258.52	$258.50	$258.50
Purchase #6	$156.86	10.528%	$173.3742	$173.37	$173.35	$173.40
Purchase #7	$20.52	11.375%	$22.8542	$22.85	$22.85	$22.90
7 purchase totals =	$848.93		$928.7383	$928.73	$928.70	$928.80