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	$46.52	7.740%	$50.1206	$50.12	$50.10	$50.10
Purchase #2	$158.99	3.830%	$165.0793	$165.08	$165.10	$165.10
Purchase #3	$40.53	12.113%	$45.4394	$45.44	$45.45	$45.40
Purchase #4	$178.93	7.552%	$192.4428	$192.44	$192.45	$192.40
Purchase #5	$6.83	8.146%	$7.3864	$7.39	$7.40	$7.40
Purchase #6	$32.29	3.405%	$33.3895	$33.39	$33.40	$33.40
Purchase #7	$203.72	3.457%	$210.7626	$210.76	$210.75	$210.80
7 purchase totals =	$667.81		$704.6206	$704.62	$704.65	$704.60