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	$9.46	13.691%	$10.7552	$10.76	$10.75	$10.80
Purchase #2	$42.89	4.347%	$44.7544	$44.75	$44.75	$44.80
Purchase #3	$209.92	7.866%	$226.4323	$226.43	$226.45	$226.40
Purchase #4	$223.42	4.492%	$233.456	$233.46	$233.45	$233.50
Purchase #5	$192.59	9.287%	$210.4758	$210.48	$210.50	$210.50
Purchase #6	$64.42	11.739%	$71.9823	$71.98	$72.00	$72.00
Purchase #7	$154.53	9.234%	$168.7993	$168.80	$168.80	$168.80
7 purchase totals =	$897.23		$966.6553	$966.66	$966.70	$966.80