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	$91.56	6.741%	$97.7321	$97.73	$97.75	$97.70
Purchase #2	$175.94	3.823%	$182.6662	$182.67	$182.65	$182.70
Purchase #3	$223.54	13.578%	$253.8923	$253.89	$253.90	$253.90
Purchase #4	$18.59	8.660%	$20.1999	$20.20	$20.20	$20.20
Purchase #5	$170.73	6.588%	$181.9777	$181.98	$182.00	$182.00
Purchase #6	$91.34	12.136%	$102.425	$102.43	$102.45	$102.40
Purchase #7	$199.85	11.350%	$222.533	$222.53	$222.55	$222.50
7 purchase totals =	$971.55		$1,061.4262	$1,061.43	$1,061.50	$1,061.40