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	$146.41	11.543%	$163.3101	$163.31	$163.30	$163.30
Purchase #2	$132.55	13.764%	$150.7942	$150.79	$150.80	$150.80
Purchase #3	$126.74	3.579%	$131.276	$131.28	$131.30	$131.30
Purchase #4	$129.32	11.527%	$144.2267	$144.23	$144.25	$144.20
Purchase #5	$150.71	11.464%	$167.9874	$167.99	$168.00	$168.00
Purchase #6	$49.38	6.165%	$52.4243	$52.42	$52.40	$52.40
Purchase #7	$37.78	9.360%	$41.3162	$41.32	$41.30	$41.30
7 purchase totals =	$772.89		$851.3349	$851.34	$851.35	$851.30