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	$56.68	4.836%	$59.421	$59.42	$59.40	$59.40
Purchase #2	$89.68	13.179%	$101.4989	$101.50	$101.50	$101.50
Purchase #3	$160.31	13.689%	$182.2548	$182.25	$182.25	$182.30
Purchase #4	$111.96	7.708%	$120.5899	$120.59	$120.60	$120.60
Purchase #5	$231.76	5.286%	$244.0108	$244.01	$244.00	$244.00
Purchase #6	$44.50	6.181%	$47.2505	$47.25	$47.25	$47.30
Purchase #7	$67.25	13.267%	$76.1721	$76.17	$76.15	$76.20
7 purchase totals =	$762.14		$831.1980	$831.19	$831.15	$831.30