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	$151.55	3.482%	$156.827	$156.83	$156.85	$156.80
Purchase #2	$64.73	9.588%	$70.9363	$70.94	$70.95	$70.90
Purchase #3	$105.91	6.304%	$112.5866	$112.59	$112.60	$112.60
Purchase #4	$192.39	6.802%	$205.4764	$205.48	$205.50	$205.50
Purchase #5	$201.54	3.835%	$209.2691	$209.27	$209.25	$209.30
Purchase #6	$70.92	8.300%	$76.8064	$76.81	$76.80	$76.80
Purchase #7	$129.66	11.395%	$144.4348	$144.43	$144.45	$144.40
7 purchase totals =	$916.70		$976.3366	$976.35	$976.40	$976.30