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	$188.64	10.374%	$208.2095	$208.21	$208.20	$208.20
Purchase #2	$149.76	8.463%	$162.4342	$162.43	$162.45	$162.40
Purchase #3	$83.98	7.185%	$90.014	$90.01	$90.00	$90.00
Purchase #4	$214.87	11.715%	$240.042	$240.04	$240.05	$240.00
Purchase #5	$135.44	9.722%	$148.6075	$148.61	$148.60	$148.60
Purchase #6	$202.85	7.610%	$218.2869	$218.29	$218.30	$218.30
Purchase #7	$33.51	12.363%	$37.6528	$37.65	$37.65	$37.70
7 purchase totals =	$1,009.05		$1,105.2469	$1,105.24	$1,105.25	$1,105.20