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	$135.84	12.578%	$152.926	$152.93	$152.95	$152.90
Purchase #2	$166.76	12.303%	$187.2765	$187.28	$187.30	$187.30
Purchase #3	$241.28	9.801%	$264.9279	$264.93	$264.95	$264.90
Purchase #4	$18.79	3.658%	$19.4773	$19.48	$19.50	$19.50
Purchase #5	$90.25	11.228%	$100.3833	$100.38	$100.40	$100.40
Purchase #6	$221.59	9.862%	$243.4432	$243.44	$243.45	$243.40
Purchase #7	$18.77	13.747%	$21.3503	$21.35	$21.35	$21.40
7 purchase totals =	$893.28		$989.7845	$989.79	$989.90	$989.80