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	$226.51	3.688%	$234.8637	$234.86	$234.85	$234.90
Purchase #2	$95.26	8.481%	$103.339	$103.34	$103.35	$103.30
Purchase #3	$86.29	3.261%	$89.1039	$89.10	$89.10	$89.10
Purchase #4	$178.65	12.226%	$200.4917	$200.49	$200.50	$200.50
Purchase #5	$153.59	13.664%	$174.5765	$174.58	$174.60	$174.60
Purchase #6	$187.36	5.108%	$196.9303	$196.93	$196.95	$196.90
Purchase #7	$165.36	10.677%	$183.0155	$183.02	$183.00	$183.00
7 purchase totals =	$1,093.02		$1,182.3206	$1,182.32	$1,182.35	$1,182.30