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	$92.66	9.785%	$101.7268	$101.73	$101.75	$101.70
Purchase #2	$99.78	13.738%	$113.4878	$113.49	$113.50	$113.50
Purchase #3	$64.89	11.483%	$72.3413	$72.34	$72.35	$72.30
Purchase #4	$107.46	3.504%	$111.2254	$111.23	$111.25	$111.20
Purchase #5	$182.80	6.470%	$194.6272	$194.63	$194.65	$194.60
Purchase #6	$121.41	5.546%	$128.1434	$128.14	$128.15	$128.10
Purchase #7	$229.25	8.441%	$248.601	$248.60	$248.60	$248.60
7 purchase totals =	$898.25		$970.1529	$970.16	$970.25	$970.00