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	$32.25	11.107%	$35.832	$35.83	$35.85	$35.80
Purchase #2	$246.57	13.808%	$280.6164	$280.62	$280.60	$280.60
Purchase #3	$245.94	9.389%	$269.0313	$269.03	$269.05	$269.00
Purchase #4	$232.41	3.405%	$240.3236	$240.32	$240.30	$240.30
Purchase #5	$90.50	12.196%	$101.5374	$101.54	$101.55	$101.50
Purchase #6	$213.57	7.650%	$229.9081	$229.91	$229.90	$229.90
Purchase #7	$15.76	11.235%	$17.5306	$17.53	$17.55	$17.50
7 purchase totals =	$1,077.00		$1,174.7794	$1,174.78	$1,174.80	$1,174.60