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	$250.42	4.816%	$262.4802	$262.48	$262.50	$262.50
Purchase #2	$51.55	3.249%	$53.2249	$53.22	$53.20	$53.20
Purchase #3	$173.43	11.216%	$192.8819	$192.88	$192.90	$192.90
Purchase #4	$220.76	9.470%	$241.666	$241.67	$241.65	$241.70
Purchase #5	$180.80	7.232%	$193.8755	$193.88	$193.90	$193.90
Purchase #6	$187.55	4.778%	$196.5111	$196.51	$196.50	$196.50
Purchase #7	$19.41	11.585%	$21.6586	$21.66	$21.65	$21.70
7 purchase totals =	$1,083.92		$1,162.2982	$1,162.30	$1,162.30	$1,162.40