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	$59.53	9.478%	$65.1723	$65.17	$65.15	$65.20
Purchase #2	$54.46	8.369%	$59.0178	$59.02	$59.00	$59.00
Purchase #3	$90.25	8.666%	$98.0711	$98.07	$98.05	$98.10
Purchase #4	$131.38	13.778%	$149.4815	$149.48	$149.50	$149.50
Purchase #5	$250.43	10.624%	$277.0357	$277.04	$277.05	$277.00
Purchase #6	$187.79	11.543%	$209.4666	$209.47	$209.45	$209.50
Purchase #7	$6.66	12.809%	$7.5131	$7.51	$7.50	$7.50
7 purchase totals =	$780.50		$865.7581	$865.76	$865.70	$865.80