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	$123.76	3.347%	$127.9022	$127.90	$127.90	$127.90
Purchase #2	$203.67	3.336%	$210.4644	$210.46	$210.45	$210.50
Purchase #3	$57.31	13.606%	$65.1076	$65.11	$65.10	$65.10
Purchase #4	$20.97	6.147%	$22.259	$22.26	$22.25	$22.30
Purchase #5	$37.89	13.852%	$43.1385	$43.14	$43.15	$43.10
Purchase #6	$105.97	8.360%	$114.8291	$114.83	$114.85	$114.80
Purchase #7	$135.64	12.167%	$152.1433	$152.14	$152.15	$152.10
7 purchase totals =	$685.21		$735.8441	$735.84	$735.85	$735.80