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	$62.83	13.472%	$71.2945	$71.29	$71.30	$71.30
Purchase #2	$81.81	9.557%	$89.6286	$89.63	$89.65	$89.60
Purchase #3	$149.39	7.587%	$160.7242	$160.72	$160.70	$160.70
Purchase #4	$96.57	13.402%	$109.5123	$109.51	$109.50	$109.50
Purchase #5	$195.77	12.260%	$219.7714	$219.77	$219.75	$219.80
Purchase #6	$214.74	5.167%	$225.8356	$225.84	$225.85	$225.80
Purchase #7	$174.70	5.676%	$184.616	$184.62	$184.60	$184.60
7 purchase totals =	$975.81		$1,061.3826	$1,061.38	$1,061.35	$1,061.30