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	$223.73	4.200%	$233.1267	$233.13	$233.15	$233.10
Purchase #2	$210.61	5.592%	$222.3873	$222.39	$222.40	$222.40
Purchase #3	$169.82	3.262%	$175.3595	$175.36	$175.35	$175.40
Purchase #4	$41.28	12.299%	$46.357	$46.36	$46.35	$46.40
Purchase #5	$20.46	10.724%	$22.6541	$22.65	$22.65	$22.70
Purchase #6	$141.45	4.830%	$148.282	$148.28	$148.30	$148.30
Purchase #7	$37.69	7.853%	$40.6498	$40.65	$40.65	$40.60
7 purchase totals =	$845.04		$888.8164	$888.82	$888.85	$888.90