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	$43.50	7.716%	$46.8565	$46.86	$46.85	$46.90
Purchase #2	$222.27	3.427%	$229.8872	$229.89	$229.90	$229.90
Purchase #3	$229.39	9.234%	$250.5719	$250.57	$250.55	$250.60
Purchase #4	$134.54	5.238%	$141.5872	$141.59	$141.60	$141.60
Purchase #5	$176.38	8.706%	$191.7356	$191.74	$191.75	$191.70
Purchase #6	$43.30	4.663%	$45.3191	$45.32	$45.30	$45.30
Purchase #7	$191.89	8.344%	$207.9013	$207.90	$207.90	$207.90
7 purchase totals =	$1,041.27		$1,113.8588	$1,113.87	$1,113.85	$1,113.90