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	$169.33	6.662%	$180.6108	$180.61	$180.60	$180.60
Purchase #2	$169.42	10.127%	$186.5772	$186.58	$186.60	$186.60
Purchase #3	$235.96	13.566%	$267.9703	$267.97	$267.95	$268.00
Purchase #4	$75.55	10.455%	$83.4488	$83.45	$83.45	$83.40
Purchase #5	$56.28	6.567%	$59.9759	$59.98	$60.00	$60.00
Purchase #6	$6.59	13.421%	$7.4744	$7.47	$7.45	$7.50
Purchase #7	$189.38	13.778%	$215.4728	$215.47	$215.45	$215.50
7 purchase totals =	$902.51		$1,001.5302	$1,001.53	$1,001.50	$1,001.60