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	$219.53	8.792%	$238.8311	$238.83	$238.85	$238.80
Purchase #2	$174.86	13.294%	$198.1059	$198.11	$198.10	$198.10
Purchase #3	$72.56	7.660%	$78.1181	$78.12	$78.10	$78.10
Purchase #4	$227.60	7.824%	$245.4074	$245.41	$245.40	$245.40
Purchase #5	$212.98	12.803%	$240.2478	$240.25	$240.25	$240.20
Purchase #6	$27.42	6.161%	$29.1093	$29.11	$29.10	$29.10
Purchase #7	$220.72	6.517%	$235.1043	$235.10	$235.10	$235.10
7 purchase totals =	$1,155.67		$1,264.9239	$1,264.93	$1,264.90	$1,264.80