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	$112.74	13.864%	$128.3703	$128.37	$128.35	$128.40
Purchase #2	$193.81	13.188%	$219.3697	$219.37	$219.35	$219.40
Purchase #3	$225.89	7.538%	$242.9176	$242.92	$242.90	$242.90
Purchase #4	$199.41	5.480%	$210.3377	$210.34	$210.35	$210.30
Purchase #5	$87.78	12.796%	$99.0123	$99.01	$99.00	$99.00
Purchase #6	$136.82	5.476%	$144.3123	$144.31	$144.30	$144.30
Purchase #7	$214.49	5.132%	$225.4976	$225.50	$225.50	$225.50
7 purchase totals =	$1,170.94		$1,269.8175	$1,269.82	$1,269.75	$1,269.80