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	$170.92	6.455%	$181.9529	$181.95	$181.95	$182.00
Purchase #2	$80.99	10.661%	$89.6243	$89.62	$89.60	$89.60
Purchase #3	$164.71	11.339%	$183.3865	$183.39	$183.40	$183.40
Purchase #4	$149.51	12.734%	$168.5486	$168.55	$168.55	$168.50
Purchase #5	$59.27	9.641%	$64.9842	$64.98	$65.00	$65.00
Purchase #6	$198.65	8.505%	$215.5452	$215.55	$215.55	$215.50
Purchase #7	$52.66	7.478%	$56.5979	$56.60	$56.60	$56.60
7 purchase totals =	$876.71		$960.6396	$960.64	$960.65	$960.60