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	$160.63	9.500%	$175.8899	$175.89	$175.90	$175.90
Purchase #2	$138.76	9.800%	$152.3585	$152.36	$152.35	$152.40
Purchase #3	$131.39	11.375%	$146.3356	$146.34	$146.35	$146.30
Purchase #4	$13.88	13.171%	$15.7081	$15.71	$15.70	$15.70
Purchase #5	$67.62	6.356%	$71.9179	$71.92	$71.90	$71.90
Purchase #6	$109.90	4.482%	$114.8257	$114.83	$114.85	$114.80
Purchase #7	$168.74	7.496%	$181.3888	$181.39	$181.40	$181.40
7 purchase totals =	$790.92		$858.4245	$858.44	$858.45	$858.40