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	$167.91	8.399%	$182.0128	$182.01	$182.00	$182.00
Purchase #2	$49.73	13.766%	$56.5758	$56.58	$56.60	$56.60
Purchase #3	$201.32	10.507%	$222.4727	$222.47	$222.45	$222.50
Purchase #4	$205.89	6.696%	$219.6764	$219.68	$219.70	$219.70
Purchase #5	$44.90	7.732%	$48.3717	$48.37	$48.35	$48.40
Purchase #6	$230.49	7.713%	$248.2677	$248.27	$248.25	$248.30
Purchase #7	$38.63	11.759%	$43.1725	$43.17	$43.15	$43.20
7 purchase totals =	$938.87		$1,020.5496	$1,020.55	$1,020.50	$1,020.70