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	$246.84	6.372%	$262.5686	$262.57	$262.55	$262.60
Purchase #2	$238.39	7.102%	$255.3205	$255.32	$255.30	$255.30
Purchase #3	$210.25	13.317%	$238.249	$238.25	$238.25	$238.20
Purchase #4	$33.72	4.123%	$35.1103	$35.11	$35.10	$35.10
Purchase #5	$209.82	6.665%	$223.8045	$223.80	$223.80	$223.80
Purchase #6	$206.34	8.503%	$223.8851	$223.89	$223.90	$223.90
Purchase #7	$76.83	12.596%	$86.5075	$86.51	$86.50	$86.50
7 purchase totals =	$1,222.19		$1,325.4455	$1,325.45	$1,325.40	$1,325.40