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	$49.82	3.223%	$51.4257	$51.43	$51.45	$51.40
Purchase #2	$244.46	4.417%	$255.2578	$255.26	$255.25	$255.30
Purchase #3	$93.74	11.483%	$104.5042	$104.50	$104.50	$104.50
Purchase #4	$169.91	9.177%	$185.5026	$185.50	$185.50	$185.50
Purchase #5	$201.98	3.829%	$209.7138	$209.71	$209.70	$209.70
Purchase #6	$250.31	11.855%	$279.9843	$279.98	$280.00	$280.00
Purchase #7	$152.79	11.331%	$170.1026	$170.10	$170.10	$170.10
7 purchase totals =	$1,163.01		$1,256.4910	$1,256.48	$1,256.50	$1,256.50