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	$109.31	4.717%	$114.4662	$114.47	$114.45	$114.50
Purchase #2	$64.79	4.651%	$67.8034	$67.80	$67.80	$67.80
Purchase #3	$243.57	9.473%	$266.6434	$266.64	$266.65	$266.60
Purchase #4	$200.73	13.278%	$227.3829	$227.38	$227.40	$227.40
Purchase #5	$98.75	9.644%	$108.2735	$108.27	$108.25	$108.30
Purchase #6	$76.72	11.414%	$85.4768	$85.48	$85.50	$85.50
Purchase #7	$105.37	7.790%	$113.5783	$113.58	$113.60	$113.60
7 purchase totals =	$899.24		$983.6245	$983.62	$983.65	$983.70