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	$105.30	11.419%	$117.3242	$117.32	$117.30	$117.30
Purchase #2	$177.74	13.585%	$201.886	$201.89	$201.90	$201.90
Purchase #3	$32.82	12.453%	$36.9071	$36.91	$36.90	$36.90
Purchase #4	$214.55	11.165%	$238.5045	$238.50	$238.50	$238.50
Purchase #5	$90.31	13.533%	$102.5317	$102.53	$102.55	$102.50
Purchase #6	$49.36	11.174%	$54.8755	$54.88	$54.90	$54.90
Purchase #7	$196.34	12.622%	$221.122	$221.12	$221.10	$221.10
7 purchase totals =	$866.42		$973.1510	$973.15	$973.15	$973.10