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	$150.31	8.275%	$162.7482	$162.75	$162.75	$162.70
Purchase #2	$220.70	4.194%	$229.9562	$229.96	$229.95	$230.00
Purchase #3	$129.58	11.511%	$144.496	$144.50	$144.50	$144.50
Purchase #4	$32.58	10.193%	$35.9009	$35.90	$35.90	$35.90
Purchase #5	$215.55	4.798%	$225.8921	$225.89	$225.90	$225.90
Purchase #6	$53.35	12.380%	$59.9547	$59.95	$59.95	$60.00
Purchase #7	$113.36	3.570%	$117.407	$117.41	$117.40	$117.40
7 purchase totals =	$915.43		$976.3551	$976.36	$976.35	$976.40