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	$219.56	3.802%	$227.9077	$227.91	$227.90	$227.90
Purchase #2	$137.25	11.721%	$153.3371	$153.34	$153.35	$153.30
Purchase #3	$146.78	10.191%	$161.7383	$161.74	$161.75	$161.70
Purchase #4	$128.57	13.173%	$145.5065	$145.51	$145.50	$145.50
Purchase #5	$209.86	4.751%	$219.8304	$219.83	$219.85	$219.80
Purchase #6	$49.68	6.525%	$52.9216	$52.92	$52.90	$52.90
Purchase #7	$41.71	8.219%	$45.1381	$45.14	$45.15	$45.10
7 purchase totals =	$933.41		$1,006.3797	$1,006.39	$1,006.40	$1,006.20