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	$146.90	11.569%	$163.8949	$163.89	$163.90	$163.90
Purchase #2	$150.46	3.389%	$155.5591	$155.56	$155.55	$155.60
Purchase #3	$51.41	9.544%	$56.3166	$56.32	$56.30	$56.30
Purchase #4	$20.89	6.195%	$22.1841	$22.18	$22.20	$22.20
Purchase #5	$53.71	10.124%	$59.1476	$59.15	$59.15	$59.10
Purchase #6	$216.73	12.527%	$243.8798	$243.88	$243.90	$243.90
Purchase #7	$223.38	8.468%	$242.2958	$242.30	$242.30	$242.30
7 purchase totals =	$863.48		$943.2779	$943.28	$943.30	$943.30