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	$68.67	11.639%	$76.6625	$76.66	$76.65	$76.70
Purchase #2	$244.96	7.432%	$263.1654	$263.17	$263.15	$263.20
Purchase #3	$7.93	8.814%	$8.629	$8.63	$8.65	$8.60
Purchase #4	$90.88	10.743%	$100.6432	$100.64	$100.65	$100.60
Purchase #5	$117.80	7.836%	$127.0308	$127.03	$127.05	$127.00
Purchase #6	$102.93	12.715%	$116.0175	$116.02	$116.00	$116.00
Purchase #7	$112.83	13.344%	$127.886	$127.89	$127.90	$127.90
7 purchase totals =	$746.00		$820.0344	$820.04	$820.05	$820.00