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	$217.95	8.835%	$237.2059	$237.21	$237.20	$237.20
Purchase #2	$169.65	6.339%	$180.4041	$180.40	$180.40	$180.40
Purchase #3	$147.36	3.496%	$152.5117	$152.51	$152.50	$152.50
Purchase #4	$164.98	12.304%	$185.2791	$185.28	$185.30	$185.30
Purchase #5	$48.31	6.187%	$51.2989	$51.30	$51.30	$51.30
Purchase #6	$146.97	8.445%	$159.3816	$159.38	$159.40	$159.40
Purchase #7	$185.72	12.182%	$208.3444	$208.34	$208.35	$208.30
7 purchase totals =	$1,080.94		$1,174.4257	$1,174.42	$1,174.45	$1,174.40