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	$43.44	9.299%	$47.4795	$47.48	$47.50	$47.50
Purchase #2	$199.33	11.294%	$221.8423	$221.84	$221.85	$221.80
Purchase #3	$41.50	9.481%	$45.4346	$45.43	$45.45	$45.40
Purchase #4	$155.78	13.114%	$176.209	$176.21	$176.20	$176.20
Purchase #5	$39.30	8.860%	$42.782	$42.78	$42.80	$42.80
Purchase #6	$238.93	12.592%	$269.0161	$269.02	$269.00	$269.00
Purchase #7	$168.47	13.776%	$191.6784	$191.68	$191.70	$191.70
7 purchase totals =	$886.75		$994.4419	$994.44	$994.50	$994.40