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	$160.37	7.388%	$172.2181	$172.22	$172.20	$172.20
Purchase #2	$19.60	4.850%	$20.5506	$20.55	$20.55	$20.60
Purchase #3	$88.47	12.309%	$99.3598	$99.36	$99.35	$99.40
Purchase #4	$86.65	8.349%	$93.8844	$93.88	$93.90	$93.90
Purchase #5	$86.62	13.113%	$97.9785	$97.98	$98.00	$98.00
Purchase #6	$82.77	13.690%	$94.1012	$94.10	$94.10	$94.10
Purchase #7	$200.86	8.123%	$217.1759	$217.18	$217.20	$217.20
7 purchase totals =	$725.34		$795.2685	$795.27	$795.30	$795.40