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	$135.75	3.664%	$140.7239	$140.72	$140.70	$140.70
Purchase #2	$156.42	13.132%	$176.9611	$176.96	$176.95	$177.00
Purchase #3	$83.66	8.164%	$90.49	$90.49	$90.50	$90.50
Purchase #4	$154.81	3.168%	$159.7144	$159.71	$159.70	$159.70
Purchase #5	$131.67	13.780%	$149.8141	$149.81	$149.80	$149.80
Purchase #6	$168.25	6.791%	$179.6759	$179.68	$179.70	$179.70
Purchase #7	$221.25	5.709%	$233.8812	$233.88	$233.90	$233.90
7 purchase totals =	$1,051.81		$1,131.2606	$1,131.25	$1,131.25	$1,131.30