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	$60.60	4.821%	$63.5215	$63.52	$63.50	$63.50
Purchase #2	$50.40	3.708%	$52.2688	$52.27	$52.25	$52.30
Purchase #3	$230.45	6.641%	$245.7542	$245.75	$245.75	$245.80
Purchase #4	$150.38	3.483%	$155.6177	$155.62	$155.60	$155.60
Purchase #5	$67.44	5.614%	$71.2261	$71.23	$71.25	$71.20
Purchase #6	$74.40	12.209%	$83.4835	$83.48	$83.50	$83.50
Purchase #7	$137.35	12.501%	$154.5201	$154.52	$154.50	$154.50
7 purchase totals =	$771.02		$826.3919	$826.39	$826.35	$826.40