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	$67.33	9.106%	$73.4611	$73.46	$73.45	$73.50
Purchase #2	$62.51	6.675%	$66.6825	$66.68	$66.70	$66.70
Purchase #3	$50.63	5.394%	$53.361	$53.36	$53.35	$53.40
Purchase #4	$81.55	8.618%	$88.578	$88.58	$88.60	$88.60
Purchase #5	$69.76	12.398%	$78.4088	$78.41	$78.40	$78.40
Purchase #6	$158.76	5.334%	$167.2283	$167.23	$167.25	$167.20
Purchase #7	$85.41	7.835%	$92.1019	$92.10	$92.10	$92.10
7 purchase totals =	$575.95		$619.8216	$619.82	$619.85	$619.90