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	$140.58	4.327%	$146.6629	$146.66	$146.65	$146.70
Purchase #2	$129.68	9.354%	$141.8103	$141.81	$141.80	$141.80
Purchase #3	$67.94	8.349%	$73.6123	$73.61	$73.60	$73.60
Purchase #4	$143.89	5.763%	$152.1824	$152.18	$152.20	$152.20
Purchase #5	$231.88	13.431%	$263.0238	$263.02	$263.00	$263.00
Purchase #6	$138.46	3.110%	$142.7661	$142.77	$142.75	$142.80
Purchase #7	$238.73	8.862%	$259.8863	$259.89	$259.90	$259.90
7 purchase totals =	$1,091.16		$1,179.9441	$1,179.94	$1,179.90	$1,180.00