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	$53.32	11.334%	$59.3633	$59.36	$59.35	$59.40
Purchase #2	$118.37	6.727%	$126.3327	$126.33	$126.35	$126.30
Purchase #3	$209.64	11.429%	$233.5998	$233.60	$233.60	$233.60
Purchase #4	$71.76	10.747%	$79.472	$79.47	$79.45	$79.50
Purchase #5	$114.58	10.416%	$126.5147	$126.51	$126.50	$126.50
Purchase #6	$160.25	9.807%	$175.9657	$175.97	$175.95	$176.00
Purchase #7	$26.52	11.569%	$29.5881	$29.59	$29.60	$29.60
7 purchase totals =	$754.44		$830.8363	$830.83	$830.80	$830.90