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	$147.28	9.531%	$161.3173	$161.32	$161.30	$161.30
Purchase #2	$169.35	13.563%	$192.3189	$192.32	$192.30	$192.30
Purchase #3	$216.48	7.381%	$232.4584	$232.46	$232.45	$232.50
Purchase #4	$196.34	11.842%	$219.5906	$219.59	$219.60	$219.60
Purchase #5	$25.71	13.532%	$29.1891	$29.19	$29.20	$29.20
Purchase #6	$56.98	3.712%	$59.0951	$59.10	$59.10	$59.10
Purchase #7	$40.38	7.717%	$43.4961	$43.50	$43.50	$43.50
7 purchase totals =	$852.52		$937.4655	$937.48	$937.45	$937.50