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	$74.84	11.615%	$83.5327	$83.53	$83.55	$83.50
Purchase #2	$228.60	8.224%	$247.4001	$247.40	$247.40	$247.40
Purchase #3	$95.99	11.440%	$106.9713	$106.97	$106.95	$107.00
Purchase #4	$242.56	11.649%	$270.8158	$270.82	$270.80	$270.80
Purchase #5	$233.79	13.518%	$265.3937	$265.39	$265.40	$265.40
Purchase #6	$154.91	13.861%	$176.3821	$176.38	$176.40	$176.40
Purchase #7	$139.58	7.471%	$150.008	$150.01	$150.00	$150.00
7 purchase totals =	$1,170.27		$1,300.5037	$1,300.50	$1,300.50	$1,300.50