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	$207.40	4.345%	$216.4115	$216.41	$216.40	$216.40
Purchase #2	$165.61	11.170%	$184.1086	$184.11	$184.10	$184.10
Purchase #3	$37.89	6.176%	$40.2301	$40.23	$40.25	$40.20
Purchase #4	$194.55	3.785%	$201.9137	$201.91	$201.90	$201.90
Purchase #5	$178.47	9.443%	$195.3229	$195.32	$195.30	$195.30
Purchase #6	$136.54	10.256%	$150.5435	$150.54	$150.55	$150.50
Purchase #7	$26.96	9.820%	$29.6075	$29.61	$29.60	$29.60
7 purchase totals =	$947.42		$1,018.1378	$1,018.13	$1,018.10	$1,018.00