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	$169.74	12.429%	$190.837	$190.84	$190.85	$190.80
Purchase #2	$75.64	3.402%	$78.2133	$78.21	$78.20	$78.20
Purchase #3	$149.62	11.292%	$166.5151	$166.52	$166.50	$166.50
Purchase #4	$200.53	3.107%	$206.7605	$206.76	$206.75	$206.80
Purchase #5	$177.44	6.383%	$188.766	$188.77	$188.75	$188.80
Purchase #6	$165.45	4.263%	$172.5031	$172.50	$172.50	$172.50
Purchase #7	$112.84	6.544%	$120.2242	$120.22	$120.20	$120.20
7 purchase totals =	$1,051.26		$1,123.8192	$1,123.82	$1,123.75	$1,123.80