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	$227.70	8.594%	$247.2685	$247.27	$247.25	$247.30
Purchase #2	$6.72	12.154%	$7.5367	$7.54	$7.55	$7.50
Purchase #3	$100.34	13.466%	$113.8518	$113.85	$113.85	$113.90
Purchase #4	$29.39	8.496%	$31.887	$31.89	$31.90	$31.90
Purchase #5	$96.88	13.585%	$110.0411	$110.04	$110.05	$110.00
Purchase #6	$46.88	9.188%	$51.1873	$51.19	$51.20	$51.20
Purchase #7	$50.65	9.267%	$55.3437	$55.34	$55.35	$55.30
7 purchase totals =	$558.56		$617.1161	$617.12	$617.15	$617.10