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	$51.56	4.808%	$54.039	$54.04	$54.05	$54.00
Purchase #2	$48.64	7.536%	$52.3055	$52.31	$52.30	$52.30
Purchase #3	$147.57	9.823%	$162.0658	$162.07	$162.05	$162.10
Purchase #4	$241.86	11.348%	$269.3063	$269.31	$269.30	$269.30
Purchase #5	$158.62	4.777%	$166.1973	$166.20	$166.20	$166.20
Purchase #6	$157.60	4.421%	$164.5675	$164.57	$164.55	$164.60
Purchase #7	$228.70	11.388%	$254.7444	$254.74	$254.75	$254.70
7 purchase totals =	$1,034.55		$1,123.2258	$1,123.24	$1,123.20	$1,123.20