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	$192.80	6.141%	$204.6398	$204.64	$204.65	$204.60
Purchase #2	$62.86	4.833%	$65.898	$65.90	$65.90	$65.90
Purchase #3	$171.68	6.494%	$182.8289	$182.83	$182.85	$182.80
Purchase #4	$89.93	9.580%	$98.5453	$98.55	$98.55	$98.50
Purchase #5	$250.38	12.539%	$281.7751	$281.78	$281.80	$281.80
Purchase #6	$61.54	7.644%	$66.2441	$66.24	$66.25	$66.20
Purchase #7	$91.50	10.208%	$100.8403	$100.84	$100.85	$100.80
7 purchase totals =	$920.69		$1,000.7715	$1,000.78	$1,000.85	$1,000.60