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	$209.95	7.134%	$224.9278	$224.93	$224.95	$224.90
Purchase #2	$12.30	12.159%	$13.7956	$13.80	$13.80	$13.80
Purchase #3	$48.27	7.501%	$51.8907	$51.89	$51.90	$51.90
Purchase #4	$44.30	3.218%	$45.7256	$45.73	$45.75	$45.70
Purchase #5	$146.61	8.693%	$159.3548	$159.35	$159.35	$159.40
Purchase #6	$58.70	9.710%	$64.3998	$64.40	$64.40	$64.40
Purchase #7	$38.30	5.437%	$40.3824	$40.38	$40.40	$40.40
7 purchase totals =	$558.43		$600.4767	$600.48	$600.55	$600.50