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	$201.94	5.319%	$212.6812	$212.68	$212.70	$212.70
Purchase #2	$157.93	10.632%	$174.7211	$174.72	$174.70	$174.70
Purchase #3	$55.98	4.425%	$58.4571	$58.46	$58.45	$58.50
Purchase #4	$198.94	11.847%	$222.5084	$222.51	$222.50	$222.50
Purchase #5	$57.32	4.118%	$59.6804	$59.68	$59.70	$59.70
Purchase #6	$175.56	8.164%	$189.8927	$189.89	$189.90	$189.90
Purchase #7	$113.56	9.145%	$123.9451	$123.95	$123.95	$123.90
7 purchase totals =	$961.23		$1,041.8860	$1,041.89	$1,041.90	$1,041.90