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	$60.50	3.169%	$62.4172	$62.42	$62.40	$62.40
Purchase #2	$15.47	10.263%	$17.0577	$17.06	$17.05	$17.10
Purchase #3	$152.50	12.865%	$172.1191	$172.12	$172.10	$172.10
Purchase #4	$131.57	4.132%	$137.0065	$137.01	$137.00	$137.00
Purchase #5	$67.72	6.164%	$71.8943	$71.89	$71.90	$71.90
Purchase #6	$66.72	12.349%	$74.9593	$74.96	$74.95	$75.00
Purchase #7	$152.53	8.477%	$165.46	$165.46	$165.45	$165.50
7 purchase totals =	$647.01		$700.9141	$700.92	$700.85	$701.00