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	$96.92	11.574%	$108.1375	$108.14	$108.15	$108.10
Purchase #2	$152.56	7.499%	$164.0005	$164.00	$164.00	$164.00
Purchase #3	$193.78	8.557%	$210.3618	$210.36	$210.35	$210.40
Purchase #4	$121.92	12.188%	$136.7796	$136.78	$136.80	$136.80
Purchase #5	$54.39	10.150%	$59.9106	$59.91	$59.90	$59.90
Purchase #6	$184.52	8.644%	$200.4699	$200.47	$200.45	$200.50
Purchase #7	$50.58	8.349%	$54.8029	$54.80	$54.80	$54.80
7 purchase totals =	$854.67		$934.4628	$934.46	$934.45	$934.50