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	$211.48	5.362%	$222.8196	$222.82	$222.80	$222.80
Purchase #2	$59.76	12.864%	$67.4475	$67.45	$67.45	$67.40
Purchase #3	$147.42	13.654%	$167.5487	$167.55	$167.55	$167.50
Purchase #4	$205.40	4.333%	$214.3	$214.30	$214.30	$214.30
Purchase #5	$213.44	8.571%	$231.7339	$231.73	$231.75	$231.70
Purchase #6	$151.69	11.234%	$168.7309	$168.73	$168.75	$168.70
Purchase #7	$220.28	6.331%	$234.2259	$234.23	$234.25	$234.20
7 purchase totals =	$1,209.47		$1,306.8065	$1,306.81	$1,306.85	$1,306.60