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	$88.41	6.581%	$94.2283	$94.23	$94.25	$94.20
Purchase #2	$201.47	10.298%	$222.2174	$222.22	$222.20	$222.20
Purchase #3	$179.53	9.643%	$196.8421	$196.84	$196.85	$196.80
Purchase #4	$246.61	5.179%	$259.3819	$259.38	$259.40	$259.40
Purchase #5	$108.47	4.852%	$113.733	$113.73	$113.75	$113.70
Purchase #6	$7.31	8.761%	$7.9504	$7.95	$7.95	$8.00
Purchase #7	$77.85	7.632%	$83.7915	$83.79	$83.80	$83.80
7 purchase totals =	$909.65		$978.1446	$978.14	$978.20	$978.10