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	$108.61	6.696%	$115.8825	$115.88	$115.90	$115.90
Purchase #2	$174.72	9.827%	$191.8897	$191.89	$191.90	$191.90
Purchase #3	$197.86	11.821%	$221.249	$221.25	$221.25	$221.20
Purchase #4	$37.94	8.859%	$41.3011	$41.30	$41.30	$41.30
Purchase #5	$57.53	11.383%	$64.0786	$64.08	$64.10	$64.10
Purchase #6	$10.29	12.127%	$11.5379	$11.54	$11.55	$11.50
Purchase #7	$85.88	10.525%	$94.9189	$94.92	$94.90	$94.90
7 purchase totals =	$672.83		$740.8577	$740.86	$740.90	$740.80