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	$78.96	10.145%	$86.9705	$86.97	$86.95	$87.00
Purchase #2	$44.76	13.456%	$50.7829	$50.78	$50.80	$50.80
Purchase #3	$103.59	10.132%	$114.0857	$114.09	$114.10	$114.10
Purchase #4	$165.76	13.711%	$188.4874	$188.49	$188.50	$188.50
Purchase #5	$69.65	10.377%	$76.8776	$76.88	$76.90	$76.90
Purchase #6	$85.39	3.102%	$88.0388	$88.04	$88.05	$88.00
Purchase #7	$146.69	8.109%	$158.5851	$158.59	$158.60	$158.60
7 purchase totals =	$694.80		$763.8280	$763.84	$763.90	$763.90