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	$64.67	3.688%	$67.055	$67.06	$67.05	$67.10
Purchase #2	$117.66	11.778%	$131.518	$131.52	$131.50	$131.50
Purchase #3	$54.92	7.458%	$59.0159	$59.02	$59.00	$59.00
Purchase #4	$219.54	7.452%	$235.9001	$235.90	$235.90	$235.90
Purchase #5	$223.29	5.156%	$234.8028	$234.80	$234.80	$234.80
Purchase #6	$208.59	9.785%	$229.0005	$229.00	$229.00	$229.00
Purchase #7	$216.84	10.266%	$239.1008	$239.10	$239.10	$239.10
7 purchase totals =	$1,105.51		$1,196.3931	$1,196.40	$1,196.35	$1,196.40