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	$23.80	6.186%	$25.2723	$25.27	$25.25	$25.30
Purchase #2	$79.90	13.782%	$90.9118	$90.91	$90.90	$90.90
Purchase #3	$117.63	11.364%	$130.9975	$131.00	$131.00	$131.00
Purchase #4	$93.93	5.260%	$98.8707	$98.87	$98.85	$98.90
Purchase #5	$34.69	8.862%	$37.7642	$37.76	$37.75	$37.80
Purchase #6	$8.51	4.378%	$8.8826	$8.88	$8.90	$8.90
Purchase #7	$83.45	7.775%	$89.9382	$89.94	$89.95	$89.90
7 purchase totals =	$441.91		$482.6373	$482.63	$482.60	$482.70