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	$93.84	12.545%	$105.6122	$105.61	$105.60	$105.60
Purchase #2	$216.76	11.487%	$241.6592	$241.66	$241.65	$241.70
Purchase #3	$121.41	6.613%	$129.4388	$129.44	$129.45	$129.40
Purchase #4	$221.38	3.692%	$229.5533	$229.55	$229.55	$229.60
Purchase #5	$96.36	13.325%	$109.2	$109.20	$109.20	$109.20
Purchase #6	$228.89	4.387%	$238.9314	$238.93	$238.95	$238.90
Purchase #7	$31.82	10.683%	$35.2193	$35.22	$35.20	$35.20
7 purchase totals =	$1,010.46		$1,089.6142	$1,089.61	$1,089.60	$1,089.60