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	$140.91	10.251%	$155.3547	$155.35	$155.35	$155.40
Purchase #2	$191.66	8.834%	$208.5912	$208.59	$208.60	$208.60
Purchase #3	$103.79	7.496%	$111.5701	$111.57	$111.55	$111.60
Purchase #4	$126.51	3.556%	$131.0087	$131.01	$131.00	$131.00
Purchase #5	$12.49	8.286%	$13.5249	$13.52	$13.50	$13.50
Purchase #6	$216.61	9.474%	$237.1316	$237.13	$237.15	$237.10
Purchase #7	$131.99	11.199%	$146.7716	$146.77	$146.75	$146.80
7 purchase totals =	$923.96		$1,003.9528	$1,003.94	$1,003.90	$1,004.00