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	$140.34	4.464%	$146.6048	$146.60	$146.60	$146.60
Purchase #2	$218.68	10.862%	$242.433	$242.43	$242.45	$242.40
Purchase #3	$67.59	5.807%	$71.515	$71.52	$71.50	$71.50
Purchase #4	$58.75	7.209%	$62.9853	$62.99	$63.00	$63.00
Purchase #5	$38.68	10.158%	$42.6091	$42.61	$42.60	$42.60
Purchase #6	$175.76	7.250%	$188.5026	$188.50	$188.50	$188.50
Purchase #7	$10.72	9.674%	$11.7571	$11.76	$11.75	$11.80
7 purchase totals =	$710.52		$766.4069	$766.41	$766.40	$766.40