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	$147.25	3.500%	$152.4038	$152.40	$152.40	$152.40
Purchase #2	$115.96	6.232%	$123.1866	$123.19	$123.20	$123.20
Purchase #3	$224.50	10.761%	$248.6584	$248.66	$248.65	$248.70
Purchase #4	$206.89	7.726%	$222.8743	$222.87	$222.85	$222.90
Purchase #5	$87.91	4.140%	$91.5495	$91.55	$91.55	$91.50
Purchase #6	$106.99	11.769%	$119.5817	$119.58	$119.60	$119.60
Purchase #7	$214.80	11.121%	$238.6879	$238.69	$238.70	$238.70
7 purchase totals =	$1,104.30		$1,196.9422	$1,196.94	$1,196.95	$1,197.00