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	$121.35	4.675%	$127.0231	$127.02	$127.00	$127.00
Purchase #2	$213.50	6.186%	$226.7071	$226.71	$226.70	$226.70
Purchase #3	$57.31	4.158%	$59.6929	$59.69	$59.70	$59.70
Purchase #4	$63.31	10.205%	$69.7708	$69.77	$69.75	$69.80
Purchase #5	$50.46	3.860%	$52.4078	$52.41	$52.40	$52.40
Purchase #6	$108.67	11.190%	$120.8302	$120.83	$120.85	$120.80
Purchase #7	$129.92	10.300%	$143.3018	$143.30	$143.30	$143.30
7 purchase totals =	$744.52		$799.7337	$799.73	$799.70	$799.70