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	$97.62	3.237%	$100.78	$100.78	$100.80	$100.80
Purchase #2	$38.61	3.846%	$40.0949	$40.09	$40.10	$40.10
Purchase #3	$172.42	7.749%	$185.7808	$185.78	$185.80	$185.80
Purchase #4	$78.61	8.366%	$85.1865	$85.19	$85.20	$85.20
Purchase #5	$77.99	11.410%	$86.8887	$86.89	$86.90	$86.90
Purchase #6	$155.63	4.527%	$162.6754	$162.68	$162.70	$162.70
Purchase #7	$160.29	9.727%	$175.8814	$175.88	$175.90	$175.90
7 purchase totals =	$781.17		$837.2877	$837.29	$837.40	$837.40