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	$59.66	4.554%	$62.3769	$62.38	$62.40	$62.40
Purchase #2	$128.57	5.395%	$135.5064	$135.51	$135.50	$135.50
Purchase #3	$30.37	7.329%	$32.5958	$32.60	$32.60	$32.60
Purchase #4	$63.50	12.790%	$71.6217	$71.62	$71.60	$71.60
Purchase #5	$219.84	11.222%	$244.5104	$244.51	$244.50	$244.50
Purchase #6	$135.36	9.654%	$148.4277	$148.43	$148.45	$148.40
Purchase #7	$92.38	13.204%	$104.5779	$104.58	$104.60	$104.60
7 purchase totals =	$729.68		$799.6168	$799.63	$799.65	$799.60