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	$92.99	11.650%	$103.8233	$103.82	$103.80	$103.80
Purchase #2	$10.57	8.513%	$11.4698	$11.47	$11.45	$11.50
Purchase #3	$55.83	9.326%	$61.0367	$61.04	$61.05	$61.00
Purchase #4	$114.75	11.649%	$128.1172	$128.12	$128.10	$128.10
Purchase #5	$76.94	11.694%	$85.9374	$85.94	$85.95	$85.90
Purchase #6	$22.36	4.688%	$23.4082	$23.41	$23.40	$23.40
Purchase #7	$76.59	12.759%	$86.3621	$86.36	$86.35	$86.40
7 purchase totals =	$450.03		$500.1547	$500.16	$500.10	$500.10