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	$157.92	6.103%	$167.5579	$167.56	$167.55	$167.60
Purchase #2	$61.89	5.722%	$65.4313	$65.43	$65.45	$65.40
Purchase #3	$159.46	3.124%	$164.4415	$164.44	$164.45	$164.40
Purchase #4	$128.63	8.190%	$139.1648	$139.16	$139.15	$139.20
Purchase #5	$59.61	10.663%	$65.9662	$65.97	$65.95	$66.00
Purchase #6	$60.89	8.365%	$65.9834	$65.98	$66.00	$66.00
Purchase #7	$183.25	10.189%	$201.9213	$201.92	$201.90	$201.90
7 purchase totals =	$811.65		$870.4664	$870.46	$870.45	$870.50