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	$164.42	11.777%	$183.7837	$183.78	$183.80	$183.80
Purchase #2	$57.88	8.349%	$62.7124	$62.71	$62.70	$62.70
Purchase #3	$107.66	4.754%	$112.7782	$112.78	$112.80	$112.80
Purchase #4	$70.59	9.404%	$77.2283	$77.23	$77.25	$77.20
Purchase #5	$151.58	4.442%	$158.3132	$158.31	$158.30	$158.30
Purchase #6	$165.48	4.319%	$172.6271	$172.63	$172.65	$172.60
Purchase #7	$167.77	8.488%	$182.0103	$182.01	$182.00	$182.00
7 purchase totals =	$885.38		$949.4532	$949.45	$949.50	$949.40