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	$134.69	13.506%	$152.8812	$152.88	$152.90	$152.90
Purchase #2	$143.78	5.728%	$152.0157	$152.02	$152.00	$152.00
Purchase #3	$188.89	8.466%	$204.8814	$204.88	$204.90	$204.90
Purchase #4	$101.66	11.545%	$113.3966	$113.40	$113.40	$113.40
Purchase #5	$126.76	12.479%	$142.5784	$142.58	$142.60	$142.60
Purchase #6	$52.41	7.598%	$56.3921	$56.39	$56.40	$56.40
Purchase #7	$125.90	9.573%	$137.9524	$137.95	$137.95	$138.00
7 purchase totals =	$874.09		$960.0978	$960.10	$960.15	$960.20