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	$116.69	12.803%	$131.6298	$131.63	$131.65	$131.60
Purchase #2	$100.69	7.601%	$108.3434	$108.34	$108.35	$108.30
Purchase #3	$33.42	6.664%	$35.6471	$35.65	$35.65	$35.60
Purchase #4	$220.80	11.573%	$246.3532	$246.35	$246.35	$246.40
Purchase #5	$53.31	11.165%	$59.2621	$59.26	$59.25	$59.30
Purchase #6	$192.66	10.774%	$213.4172	$213.42	$213.40	$213.40
Purchase #7	$36.36	12.267%	$40.8203	$40.82	$40.80	$40.80
7 purchase totals =	$753.93		$835.4731	$835.47	$835.45	$835.40