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	$172.92	10.295%	$190.7221	$190.72	$190.70	$190.70
Purchase #2	$37.31	11.273%	$41.516	$41.52	$41.50	$41.50
Purchase #3	$98.58	8.103%	$106.5679	$106.57	$106.55	$106.60
Purchase #4	$238.40	10.167%	$262.6381	$262.64	$262.65	$262.60
Purchase #5	$234.65	12.859%	$264.8236	$264.82	$264.80	$264.80
Purchase #6	$63.45	9.754%	$69.6389	$69.64	$69.65	$69.60
Purchase #7	$133.60	6.218%	$141.9072	$141.91	$141.90	$141.90
7 purchase totals =	$978.91		$1,077.8138	$1,077.82	$1,077.75	$1,077.70