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	$82.36	7.254%	$88.3344	$88.33	$88.35	$88.30
Purchase #2	$38.60	4.561%	$40.3605	$40.36	$40.35	$40.40
Purchase #3	$91.38	8.754%	$99.3794	$99.38	$99.40	$99.40
Purchase #4	$107.35	11.425%	$119.6147	$119.61	$119.60	$119.60
Purchase #5	$200.88	10.837%	$222.6494	$222.65	$222.65	$222.60
Purchase #6	$148.82	11.731%	$166.2781	$166.28	$166.30	$166.30
Purchase #7	$30.62	7.648%	$32.9618	$32.96	$32.95	$33.00
7 purchase totals =	$700.01		$769.5783	$769.57	$769.60	$769.60