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	$192.34	6.784%	$205.3883	$205.39	$205.40	$205.40
Purchase #2	$180.48	10.678%	$199.7517	$199.75	$199.75	$199.80
Purchase #3	$12.36	7.126%	$13.2408	$13.24	$13.25	$13.20
Purchase #4	$99.82	11.836%	$111.6347	$111.63	$111.65	$111.60
Purchase #5	$85.82	11.206%	$95.437	$95.44	$95.45	$95.40
Purchase #6	$26.82	10.824%	$29.723	$29.72	$29.70	$29.70
Purchase #7	$200.90	11.757%	$224.5198	$224.52	$224.50	$224.50
7 purchase totals =	$798.54		$879.6953	$879.69	$879.70	$879.60