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	$111.65	4.730%	$116.931	$116.93	$116.95	$116.90
Purchase #2	$238.58	5.134%	$250.8287	$250.83	$250.85	$250.80
Purchase #3	$132.93	5.700%	$140.507	$140.51	$140.50	$140.50
Purchase #4	$99.85	7.310%	$107.149	$107.15	$107.15	$107.10
Purchase #5	$25.33	9.151%	$27.6479	$27.65	$27.65	$27.60
Purchase #6	$94.84	11.515%	$105.7608	$105.76	$105.75	$105.80
Purchase #7	$12.78	7.143%	$13.6929	$13.69	$13.70	$13.70
7 purchase totals =	$715.96		$762.5173	$762.52	$762.55	$762.40