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	$87.68	13.275%	$99.3195	$99.32	$99.30	$99.30
Purchase #2	$211.51	5.585%	$223.3228	$223.32	$223.30	$223.30
Purchase #3	$193.45	10.612%	$213.9789	$213.98	$214.00	$214.00
Purchase #4	$46.81	12.767%	$52.7862	$52.79	$52.80	$52.80
Purchase #5	$131.44	3.580%	$136.1456	$136.15	$136.15	$136.10
Purchase #6	$213.81	9.321%	$233.7392	$233.74	$233.75	$233.70
Purchase #7	$137.30	6.219%	$145.8387	$145.84	$145.85	$145.80
7 purchase totals =	$1,022.00		$1,105.1309	$1,105.14	$1,105.15	$1,105.00