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	$182.96	4.721%	$191.5975	$191.60	$191.60	$191.60
Purchase #2	$250.87	8.709%	$272.7183	$272.72	$272.70	$272.70
Purchase #3	$88.68	8.840%	$96.5193	$96.52	$96.50	$96.50
Purchase #4	$55.73	5.492%	$58.7907	$58.79	$58.80	$58.80
Purchase #5	$35.31	5.837%	$37.371	$37.37	$37.35	$37.40
Purchase #6	$106.88	4.242%	$111.4138	$111.41	$111.40	$111.40
Purchase #7	$248.61	9.871%	$273.1503	$273.15	$273.15	$273.20
7 purchase totals =	$969.04		$1,041.5609	$1,041.56	$1,041.50	$1,041.60