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	$160.89	13.471%	$182.5635	$182.56	$182.55	$182.60
Purchase #2	$89.76	6.561%	$95.6492	$95.65	$95.65	$95.60
Purchase #3	$124.37	7.648%	$133.8818	$133.88	$133.90	$133.90
Purchase #4	$135.74	8.867%	$147.7761	$147.78	$147.80	$147.80
Purchase #5	$39.85	7.538%	$42.8539	$42.85	$42.85	$42.90
Purchase #6	$161.25	11.123%	$179.1858	$179.19	$179.20	$179.20
Purchase #7	$169.48	7.462%	$182.1266	$182.13	$182.15	$182.10
7 purchase totals =	$881.34		$964.0369	$964.04	$964.10	$964.10