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	$40.53	10.168%	$44.6511	$44.65	$44.65	$44.70
Purchase #2	$84.92	13.431%	$96.3256	$96.33	$96.35	$96.30
Purchase #3	$148.31	13.580%	$168.4505	$168.45	$168.45	$168.50
Purchase #4	$191.57	8.735%	$208.3036	$208.30	$208.30	$208.30
Purchase #5	$86.29	5.727%	$91.2318	$91.23	$91.25	$91.20
Purchase #6	$89.84	10.336%	$99.1259	$99.13	$99.15	$99.10
Purchase #7	$141.29	13.853%	$160.8629	$160.86	$160.85	$160.90
7 purchase totals =	$782.75		$868.9514	$868.95	$869.00	$869.00