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	$153.79	8.426%	$166.7483	$166.75	$166.75	$166.70
Purchase #2	$162.30	10.299%	$179.0153	$179.02	$179.00	$179.00
Purchase #3	$200.33	13.164%	$226.7014	$226.70	$226.70	$226.70
Purchase #4	$82.83	11.217%	$92.121	$92.12	$92.10	$92.10
Purchase #5	$193.61	9.761%	$212.5083	$212.51	$212.50	$212.50
Purchase #6	$54.89	9.174%	$59.9256	$59.93	$59.95	$59.90
Purchase #7	$172.33	12.771%	$194.3383	$194.34	$194.35	$194.30
7 purchase totals =	$1,020.08		$1,131.3582	$1,131.37	$1,131.35	$1,131.20