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	$244.66	8.614%	$265.735	$265.74	$265.75	$265.70
Purchase #2	$37.39	12.514%	$42.069	$42.07	$42.05	$42.10
Purchase #3	$147.32	3.149%	$151.9591	$151.96	$151.95	$152.00
Purchase #4	$138.98	11.139%	$154.461	$154.46	$154.45	$154.50
Purchase #5	$118.47	9.664%	$129.9189	$129.92	$129.90	$129.90
Purchase #6	$88.76	5.783%	$93.893	$93.89	$93.90	$93.90
Purchase #7	$65.59	9.869%	$72.0631	$72.06	$72.05	$72.10
7 purchase totals =	$841.17		$910.0991	$910.10	$910.05	$910.20