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	$53.28	8.322%	$57.714	$57.71	$57.70	$57.70
Purchase #2	$89.49	10.131%	$98.5562	$98.56	$98.55	$98.60
Purchase #3	$18.42	6.267%	$19.5744	$19.57	$19.55	$19.60
Purchase #4	$53.34	10.839%	$59.1215	$59.12	$59.10	$59.10
Purchase #5	$139.75	6.328%	$148.5934	$148.59	$148.60	$148.60
Purchase #6	$147.95	11.216%	$164.5441	$164.54	$164.55	$164.50
Purchase #7	$140.44	9.515%	$153.8029	$153.80	$153.80	$153.80
7 purchase totals =	$642.67		$701.9065	$701.89	$701.85	$701.90