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	$30.61	9.862%	$33.6288	$33.63	$33.65	$33.60
Purchase #2	$203.40	9.781%	$223.2946	$223.29	$223.30	$223.30
Purchase #3	$83.66	10.717%	$92.6258	$92.63	$92.65	$92.60
Purchase #4	$238.71	6.656%	$254.5985	$254.60	$254.60	$254.60
Purchase #5	$153.70	8.149%	$166.225	$166.23	$166.25	$166.20
Purchase #6	$93.56	12.767%	$105.5048	$105.50	$105.50	$105.50
Purchase #7	$136.53	7.695%	$147.036	$147.04	$147.05	$147.00
7 purchase totals =	$940.17		$1,022.9135	$1,022.92	$1,023.00	$1,022.80