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	$190.74	13.272%	$216.055	$216.06	$216.05	$216.10
Purchase #2	$151.78	5.434%	$160.0277	$160.03	$160.05	$160.00
Purchase #3	$74.94	4.576%	$78.3693	$78.37	$78.35	$78.40
Purchase #4	$23.54	7.755%	$25.3655	$25.37	$25.35	$25.40
Purchase #5	$67.83	7.228%	$72.7328	$72.73	$72.75	$72.70
Purchase #6	$176.88	11.349%	$196.9541	$196.95	$196.95	$197.00
Purchase #7	$227.57	7.502%	$244.6423	$244.64	$244.65	$244.60
7 purchase totals =	$913.28		$994.1467	$994.15	$994.15	$994.20