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	$73.44	13.359%	$83.2508	$83.25	$83.25	$83.30
Purchase #2	$179.62	9.295%	$196.3157	$196.32	$196.30	$196.30
Purchase #3	$190.51	13.590%	$216.4003	$216.40	$216.40	$216.40
Purchase #4	$206.71	10.829%	$229.0946	$229.09	$229.10	$229.10
Purchase #5	$168.59	11.287%	$187.6188	$187.62	$187.60	$187.60
Purchase #6	$186.91	8.341%	$202.5002	$202.50	$202.50	$202.50
Purchase #7	$166.37	7.845%	$179.4217	$179.42	$179.40	$179.40
7 purchase totals =	$1,172.15		$1,294.6021	$1,294.60	$1,294.55	$1,294.60