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	$240.43	6.651%	$256.421	$256.42	$256.40	$256.40
Purchase #2	$35.59	10.590%	$39.359	$39.36	$39.35	$39.40
Purchase #3	$225.87	9.695%	$247.7681	$247.77	$247.75	$247.80
Purchase #4	$160.55	5.135%	$168.7942	$168.79	$168.80	$168.80
Purchase #5	$149.72	4.517%	$156.4829	$156.48	$156.50	$156.50
Purchase #6	$87.94	3.380%	$90.9124	$90.91	$90.90	$90.90
Purchase #7	$243.70	8.649%	$264.7776	$264.78	$264.80	$264.80
7 purchase totals =	$1,143.80		$1,224.5152	$1,224.51	$1,224.50	$1,224.60