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	$113.85	12.607%	$128.2031	$128.20	$128.20	$128.20
Purchase #2	$171.32	9.359%	$187.3538	$187.35	$187.35	$187.40
Purchase #3	$24.97	11.734%	$27.9	$27.90	$27.90	$27.90
Purchase #4	$153.34	10.210%	$168.996	$169.00	$169.00	$169.00
Purchase #5	$101.44	9.742%	$111.3223	$111.32	$111.30	$111.30
Purchase #6	$225.48	11.554%	$251.532	$251.53	$251.55	$251.50
Purchase #7	$185.42	11.690%	$207.0956	$207.10	$207.10	$207.10
7 purchase totals =	$975.82		$1,082.4028	$1,082.40	$1,082.40	$1,082.40