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	$113.82	11.595%	$127.0174	$127.02	$127.00	$127.00
Purchase #2	$110.90	6.197%	$117.7725	$117.77	$117.75	$117.80
Purchase #3	$102.89	6.166%	$109.2342	$109.23	$109.25	$109.20
Purchase #4	$50.62	9.558%	$55.4583	$55.46	$55.45	$55.50
Purchase #5	$106.81	12.580%	$120.2467	$120.25	$120.25	$120.20
Purchase #6	$50.25	9.214%	$54.88	$54.88	$54.90	$54.90
Purchase #7	$94.66	10.321%	$104.4299	$104.43	$104.45	$104.40
7 purchase totals =	$629.95		$689.0390	$689.04	$689.05	$689.00