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	$64.98	4.132%	$67.665	$67.67	$67.65	$67.70
Purchase #2	$196.48	11.154%	$218.3954	$218.40	$218.40	$218.40
Purchase #3	$94.72	3.391%	$97.932	$97.93	$97.95	$97.90
Purchase #4	$50.96	9.289%	$55.6937	$55.69	$55.70	$55.70
Purchase #5	$156.73	10.578%	$173.3089	$173.31	$173.30	$173.30
Purchase #6	$123.98	4.483%	$129.538	$129.54	$129.55	$129.50
Purchase #7	$209.89	6.647%	$223.8414	$223.84	$223.85	$223.80
7 purchase totals =	$897.74		$966.3744	$966.38	$966.40	$966.30