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	$47.85	13.767%	$54.4375	$54.44	$54.45	$54.40
Purchase #2	$217.69	11.345%	$242.3869	$242.39	$242.40	$242.40
Purchase #3	$199.83	9.554%	$218.9218	$218.92	$218.90	$218.90
Purchase #4	$139.32	4.285%	$145.2899	$145.29	$145.30	$145.30
Purchase #5	$203.98	4.828%	$213.8282	$213.83	$213.85	$213.80
Purchase #6	$159.47	6.501%	$169.8371	$169.84	$169.85	$169.80
Purchase #7	$213.35	9.632%	$233.8999	$233.90	$233.90	$233.90
7 purchase totals =	$1,181.49		$1,278.6013	$1,278.61	$1,278.65	$1,278.50