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	$152.53	8.859%	$166.0426	$166.04	$166.05	$166.00
Purchase #2	$180.43	4.164%	$187.9431	$187.94	$187.95	$187.90
Purchase #3	$50.52	7.789%	$54.455	$54.46	$54.45	$54.50
Purchase #4	$237.76	11.641%	$265.4376	$265.44	$265.45	$265.40
Purchase #5	$40.37	5.265%	$42.4955	$42.50	$42.50	$42.50
Purchase #6	$6.71	4.767%	$7.0299	$7.03	$7.05	$7.00
Purchase #7	$127.62	10.304%	$140.77	$140.77	$140.75	$140.80
7 purchase totals =	$795.94		$864.1737	$864.18	$864.20	$864.10