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	$213.55	12.664%	$240.594	$240.59	$240.60	$240.60
Purchase #2	$199.34	4.784%	$208.8764	$208.88	$208.90	$208.90
Purchase #3	$185.32	10.359%	$204.5173	$204.52	$204.50	$204.50
Purchase #4	$92.28	7.824%	$99.5	$99.50	$99.50	$99.50
Purchase #5	$224.83	12.636%	$253.2395	$253.24	$253.25	$253.20
Purchase #6	$247.34	6.752%	$264.0404	$264.04	$264.05	$264.00
Purchase #7	$181.33	13.503%	$205.815	$205.82	$205.80	$205.80
7 purchase totals =	$1,343.99		$1,476.5826	$1,476.59	$1,476.60	$1,476.50