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	$242.44	11.483%	$270.2794	$270.28	$270.30	$270.30
Purchase #2	$156.77	5.338%	$165.1384	$165.14	$165.15	$165.10
Purchase #3	$167.78	11.295%	$186.7308	$186.73	$186.75	$186.70
Purchase #4	$92.82	7.179%	$99.4835	$99.48	$99.50	$99.50
Purchase #5	$25.48	10.743%	$28.2173	$28.22	$28.20	$28.20
Purchase #6	$23.85	7.371%	$25.608	$25.61	$25.60	$25.60
Purchase #7	$171.39	11.205%	$190.5942	$190.59	$190.60	$190.60
7 purchase totals =	$880.53		$966.0516	$966.05	$966.10	$966.00