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	$52.25	6.519%	$55.6562	$55.66	$55.65	$55.70
Purchase #2	$50.99	3.602%	$52.8267	$52.83	$52.85	$52.80
Purchase #3	$85.45	11.854%	$95.5792	$95.58	$95.60	$95.60
Purchase #4	$245.74	6.443%	$261.573	$261.57	$261.55	$261.60
Purchase #5	$18.85	12.790%	$21.2609	$21.26	$21.25	$21.30
Purchase #6	$153.65	3.701%	$159.3366	$159.34	$159.35	$159.30
Purchase #7	$89.53	12.140%	$100.3989	$100.40	$100.40	$100.40
7 purchase totals =	$696.46		$746.6315	$746.64	$746.65	$746.70