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	$29.31	11.311%	$32.6253	$32.63	$32.65	$32.60
Purchase #2	$193.28	13.383%	$219.1467	$219.15	$219.15	$219.10
Purchase #3	$58.64	11.737%	$65.5226	$65.52	$65.50	$65.50
Purchase #4	$10.54	10.137%	$11.6084	$11.61	$11.60	$11.60
Purchase #5	$226.59	12.685%	$255.3329	$255.33	$255.35	$255.30
Purchase #6	$82.65	13.103%	$93.4796	$93.48	$93.50	$93.50
Purchase #7	$191.61	10.165%	$211.0872	$211.09	$211.10	$211.10
7 purchase totals =	$792.62		$888.8027	$888.81	$888.85	$888.70