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	$246.31	7.835%	$265.6084	$265.61	$265.60	$265.60
Purchase #2	$84.46	11.486%	$94.1611	$94.16	$94.15	$94.20
Purchase #3	$85.31	7.450%	$91.6656	$91.67	$91.65	$91.70
Purchase #4	$94.31	11.631%	$105.2792	$105.28	$105.30	$105.30
Purchase #5	$200.32	13.331%	$227.0247	$227.02	$227.00	$227.00
Purchase #6	$202.81	10.848%	$224.8108	$224.81	$224.80	$224.80
Purchase #7	$42.29	6.657%	$45.1052	$45.11	$45.10	$45.10
7 purchase totals =	$955.81		$1,053.6550	$1,053.66	$1,053.60	$1,053.70