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	$144.66	4.516%	$151.1928	$151.19	$151.20	$151.20
Purchase #2	$179.82	7.700%	$193.6661	$193.67	$193.65	$193.70
Purchase #3	$57.25	11.368%	$63.7582	$63.76	$63.75	$63.80
Purchase #4	$224.86	7.688%	$242.1472	$242.15	$242.15	$242.10
Purchase #5	$185.25	5.863%	$196.1112	$196.11	$196.10	$196.10
Purchase #6	$88.62	13.820%	$100.8673	$100.87	$100.85	$100.90
Purchase #7	$41.93	9.449%	$45.892	$45.89	$45.90	$45.90
7 purchase totals =	$922.39		$993.6348	$993.64	$993.60	$993.70