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	$30.41	11.557%	$33.9245	$33.92	$33.90	$33.90
Purchase #2	$195.96	10.440%	$216.4182	$216.42	$216.40	$216.40
Purchase #3	$40.66	11.727%	$45.4282	$45.43	$45.45	$45.40
Purchase #4	$94.75	5.210%	$99.6865	$99.69	$99.70	$99.70
Purchase #5	$71.52	10.178%	$78.7993	$78.80	$78.80	$78.80
Purchase #6	$215.71	13.685%	$245.2299	$245.23	$245.25	$245.20
Purchase #7	$50.82	9.459%	$55.6271	$55.63	$55.65	$55.60
7 purchase totals =	$699.83		$775.1137	$775.12	$775.15	$775.00