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	$243.56	10.831%	$269.94	$269.94	$269.95	$269.90
Purchase #2	$21.84	3.359%	$22.5736	$22.57	$22.55	$22.60
Purchase #3	$228.72	12.340%	$256.944	$256.94	$256.95	$256.90
Purchase #4	$161.38	6.826%	$172.3958	$172.40	$172.40	$172.40
Purchase #5	$249.75	13.569%	$283.6386	$283.64	$283.65	$283.60
Purchase #6	$71.92	8.301%	$77.8901	$77.89	$77.90	$77.90
Purchase #7	$102.44	7.273%	$109.8905	$109.89	$109.90	$109.90
7 purchase totals =	$1,079.61		$1,193.2726	$1,193.27	$1,193.30	$1,193.20