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	$52.70	4.407%	$55.0225	$55.02	$55.00	$55.00
Purchase #2	$117.90	4.834%	$123.5993	$123.60	$123.60	$123.60
Purchase #3	$82.29	4.686%	$86.1461	$86.15	$86.15	$86.10
Purchase #4	$89.80	11.853%	$100.444	$100.44	$100.45	$100.40
Purchase #5	$15.78	12.248%	$17.7127	$17.71	$17.70	$17.70
Purchase #6	$70.94	5.357%	$74.7403	$74.74	$74.75	$74.70
Purchase #7	$246.69	11.433%	$274.8941	$274.89	$274.90	$274.90
7 purchase totals =	$676.10		$732.5590	$732.55	$732.55	$732.40