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	$125.87	4.803%	$131.9155	$131.92	$131.90	$131.90
Purchase #2	$217.48	7.741%	$234.3151	$234.32	$234.30	$234.30
Purchase #3	$175.79	6.249%	$186.7751	$186.78	$186.80	$186.80
Purchase #4	$29.51	10.658%	$32.6552	$32.66	$32.65	$32.70
Purchase #5	$183.37	5.170%	$192.8502	$192.85	$192.85	$192.90
Purchase #6	$132.27	11.705%	$147.7522	$147.75	$147.75	$147.80
Purchase #7	$126.59	7.108%	$135.588	$135.59	$135.60	$135.60
7 purchase totals =	$990.88		$1,061.8513	$1,061.87	$1,061.85	$1,062.00