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	$64.67	10.382%	$71.384	$71.38	$71.40	$71.40
Purchase #2	$87.75	13.171%	$99.3076	$99.31	$99.30	$99.30
Purchase #3	$8.59	12.748%	$9.6851	$9.69	$9.70	$9.70
Purchase #4	$230.34	10.485%	$254.4911	$254.49	$254.50	$254.50
Purchase #5	$135.53	12.798%	$152.8751	$152.88	$152.90	$152.90
Purchase #6	$169.82	4.582%	$177.6012	$177.60	$177.60	$177.60
Purchase #7	$53.69	11.546%	$59.889	$59.89	$59.90	$59.90
7 purchase totals =	$750.39		$825.2331	$825.24	$825.30	$825.30