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	$197.75	5.403%	$208.4344	$208.43	$208.45	$208.40
Purchase #2	$144.36	9.408%	$157.9414	$157.94	$157.95	$157.90
Purchase #3	$146.74	3.738%	$152.2251	$152.23	$152.25	$152.20
Purchase #4	$228.55	4.515%	$238.869	$238.87	$238.85	$238.90
Purchase #5	$216.64	12.228%	$243.1307	$243.13	$243.15	$243.10
Purchase #6	$63.55	3.685%	$65.8918	$65.89	$65.90	$65.90
Purchase #7	$166.53	13.582%	$189.1481	$189.15	$189.15	$189.10
7 purchase totals =	$1,164.12		$1,255.6405	$1,255.64	$1,255.70	$1,255.50