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	$87.83	4.250%	$91.5628	$91.56	$91.55	$91.60
Purchase #2	$61.30	4.493%	$64.0542	$64.05	$64.05	$64.10
Purchase #3	$196.77	8.379%	$213.2574	$213.26	$213.25	$213.30
Purchase #4	$203.43	9.735%	$223.2339	$223.23	$223.25	$223.20
Purchase #5	$75.43	13.735%	$85.7903	$85.79	$85.80	$85.80
Purchase #6	$61.93	13.864%	$70.516	$70.52	$70.50	$70.50
Purchase #7	$246.43	12.267%	$276.6596	$276.66	$276.65	$276.70
7 purchase totals =	$933.12		$1,025.0742	$1,025.07	$1,025.05	$1,025.20