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	$168.61	4.743%	$176.6072	$176.61	$176.60	$176.60
Purchase #2	$120.44	8.617%	$130.8183	$130.82	$130.80	$130.80
Purchase #3	$79.53	7.532%	$85.5202	$85.52	$85.50	$85.50
Purchase #4	$233.50	12.600%	$262.921	$262.92	$262.90	$262.90
Purchase #5	$48.60	8.103%	$52.5381	$52.54	$52.55	$52.50
Purchase #6	$147.85	8.619%	$160.5932	$160.59	$160.60	$160.60
Purchase #7	$147.81	13.658%	$167.9979	$168.00	$168.00	$168.00
7 purchase totals =	$946.34		$1,036.9959	$1,037.00	$1,036.95	$1,036.90