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	$62.57	13.765%	$71.1828	$71.18	$71.20	$71.20
Purchase #2	$100.68	11.194%	$111.9501	$111.95	$111.95	$112.00
Purchase #3	$193.54	13.458%	$219.5866	$219.59	$219.60	$219.60
Purchase #4	$236.44	4.484%	$247.042	$247.04	$247.05	$247.00
Purchase #5	$29.99	5.792%	$31.727	$31.73	$31.75	$31.70
Purchase #6	$54.83	8.761%	$59.6337	$59.63	$59.65	$59.60
Purchase #7	$178.89	3.121%	$184.4732	$184.47	$184.45	$184.50
7 purchase totals =	$856.94		$925.5954	$925.59	$925.65	$925.60