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	$127.25	3.278%	$131.4213	$131.42	$131.40	$131.40
Purchase #2	$37.73	11.765%	$42.1689	$42.17	$42.15	$42.20
Purchase #3	$95.48	5.760%	$100.9796	$100.98	$101.00	$101.00
Purchase #4	$31.63	9.518%	$34.6405	$34.64	$34.65	$34.60
Purchase #5	$111.64	5.703%	$118.0068	$118.01	$118.00	$118.00
Purchase #6	$181.71	10.197%	$200.239	$200.24	$200.25	$200.20
Purchase #7	$145.54	9.376%	$159.1858	$159.19	$159.20	$159.20
7 purchase totals =	$730.98		$786.6419	$786.65	$786.65	$786.60