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	$6.63	6.274%	$7.046	$7.05	$7.05	$7.00
Purchase #2	$87.90	4.729%	$92.0568	$92.06	$92.05	$92.10
Purchase #3	$186.73	13.237%	$211.4475	$211.45	$211.45	$211.40
Purchase #4	$240.53	6.111%	$255.2288	$255.23	$255.25	$255.20
Purchase #5	$15.74	7.320%	$16.8922	$16.89	$16.90	$16.90
Purchase #6	$33.46	11.774%	$37.3996	$37.40	$37.40	$37.40
Purchase #7	$88.79	4.448%	$92.7394	$92.74	$92.75	$92.70
7 purchase totals =	$659.78		$712.8103	$712.82	$712.85	$712.70