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	$106.31	3.332%	$109.8522	$109.85	$109.85	$109.90
Purchase #2	$20.86	6.598%	$22.2363	$22.24	$22.25	$22.20
Purchase #3	$213.43	12.496%	$240.1002	$240.10	$240.10	$240.10
Purchase #4	$78.39	9.527%	$85.8582	$85.86	$85.85	$85.90
Purchase #5	$100.63	12.643%	$113.3527	$113.35	$113.35	$113.40
Purchase #6	$147.25	11.286%	$163.8686	$163.87	$163.85	$163.90
Purchase #7	$150.62	12.130%	$168.8902	$168.89	$168.90	$168.90
7 purchase totals =	$817.49		$904.1584	$904.16	$904.15	$904.30