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	$80.89	10.841%	$89.6593	$89.66	$89.65	$89.70
Purchase #2	$21.54	6.208%	$22.8772	$22.88	$22.90	$22.90
Purchase #3	$168.35	6.460%	$179.2254	$179.23	$179.25	$179.20
Purchase #4	$231.54	7.319%	$248.4864	$248.49	$248.50	$248.50
Purchase #5	$133.34	5.227%	$140.3097	$140.31	$140.30	$140.30
Purchase #6	$76.41	7.336%	$82.0154	$82.02	$82.00	$82.00
Purchase #7	$143.89	5.699%	$152.0903	$152.09	$152.10	$152.10
7 purchase totals =	$855.96		$914.6637	$914.68	$914.70	$914.70