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	$36.45	13.733%	$41.4557	$41.46	$41.45	$41.50
Purchase #2	$221.63	12.293%	$248.875	$248.88	$248.90	$248.90
Purchase #3	$171.88	11.144%	$191.0343	$191.03	$191.05	$191.00
Purchase #4	$244.30	4.780%	$255.9775	$255.98	$256.00	$256.00
Purchase #5	$163.82	13.170%	$185.3951	$185.40	$185.40	$185.40
Purchase #6	$229.97	8.841%	$250.3016	$250.30	$250.30	$250.30
Purchase #7	$171.82	13.192%	$194.4865	$194.49	$194.50	$194.50
7 purchase totals =	$1,239.87		$1,367.5257	$1,367.54	$1,367.60	$1,367.60