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	$61.69	5.710%	$65.2125	$65.21	$65.20	$65.20
Purchase #2	$244.38	4.864%	$256.2666	$256.27	$256.25	$256.30
Purchase #3	$157.78	4.471%	$164.8343	$164.83	$164.85	$164.80
Purchase #4	$201.62	11.800%	$225.4112	$225.41	$225.40	$225.40
Purchase #5	$211.82	3.126%	$218.4415	$218.44	$218.45	$218.40
Purchase #6	$186.41	12.827%	$210.3208	$210.32	$210.30	$210.30
Purchase #7	$122.52	7.639%	$131.8793	$131.88	$131.90	$131.90
7 purchase totals =	$1,186.22		$1,272.3662	$1,272.36	$1,272.35	$1,272.30