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	$209.52	8.661%	$227.6665	$227.67	$227.65	$227.70
Purchase #2	$62.26	3.647%	$64.5306	$64.53	$64.55	$64.50
Purchase #3	$105.54	10.117%	$116.2175	$116.22	$116.20	$116.20
Purchase #4	$39.78	7.622%	$42.812	$42.81	$42.80	$42.80
Purchase #5	$201.34	10.575%	$222.6317	$222.63	$222.65	$222.60
Purchase #6	$209.66	6.825%	$223.9693	$223.97	$223.95	$224.00
Purchase #7	$173.73	11.391%	$193.5196	$193.52	$193.50	$193.50
7 purchase totals =	$1,001.83		$1,091.3472	$1,091.35	$1,091.30	$1,091.30