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	$174.70	3.554%	$180.9088	$180.91	$180.90	$180.90
Purchase #2	$86.41	6.679%	$92.1813	$92.18	$92.20	$92.20
Purchase #3	$217.43	12.171%	$243.8934	$243.89	$243.90	$243.90
Purchase #4	$21.38	4.853%	$22.4176	$22.42	$22.40	$22.40
Purchase #5	$139.89	13.324%	$158.5289	$158.53	$158.55	$158.50
Purchase #6	$190.49	13.725%	$216.6348	$216.63	$216.65	$216.60
Purchase #7	$167.28	12.196%	$187.6815	$187.68	$187.70	$187.70
7 purchase totals =	$997.58		$1,102.2463	$1,102.24	$1,102.30	$1,102.20