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	$41.44	10.503%	$45.7924	$45.79	$45.80	$45.80
Purchase #2	$135.25	4.376%	$141.1685	$141.17	$141.15	$141.20
Purchase #3	$91.51	7.384%	$98.2671	$98.27	$98.25	$98.30
Purchase #4	$163.72	5.267%	$172.3431	$172.34	$172.35	$172.30
Purchase #5	$230.86	7.668%	$248.5623	$248.56	$248.55	$248.60
Purchase #6	$15.76	9.846%	$17.3117	$17.31	$17.30	$17.30
Purchase #7	$136.81	3.865%	$142.0977	$142.10	$142.10	$142.10
7 purchase totals =	$815.35		$865.5428	$865.54	$865.50	$865.60