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	$204.51	8.760%	$222.4251	$222.43	$222.45	$222.40
Purchase #2	$29.30	7.366%	$31.4582	$31.46	$31.45	$31.50
Purchase #3	$143.65	13.405%	$162.9063	$162.91	$162.90	$162.90
Purchase #4	$18.82	5.450%	$19.8457	$19.85	$19.85	$19.80
Purchase #5	$54.96	12.825%	$62.0086	$62.01	$62.00	$62.00
Purchase #6	$203.93	11.315%	$227.0047	$227.00	$227.00	$227.00
Purchase #7	$103.33	5.602%	$109.1185	$109.12	$109.10	$109.10
7 purchase totals =	$758.50		$834.7671	$834.78	$834.75	$834.70