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	$189.40	11.151%	$210.52	$210.52	$210.50	$210.50
Purchase #2	$171.35	7.308%	$183.8723	$183.87	$183.85	$183.90
Purchase #3	$102.96	6.330%	$109.4774	$109.48	$109.50	$109.50
Purchase #4	$111.82	6.592%	$119.1912	$119.19	$119.20	$119.20
Purchase #5	$140.35	11.763%	$156.8594	$156.86	$156.85	$156.90
Purchase #6	$34.56	4.279%	$36.0388	$36.04	$36.05	$36.00
Purchase #7	$212.97	5.449%	$224.5747	$224.57	$224.55	$224.60
7 purchase totals =	$963.41		$1,040.5338	$1,040.53	$1,040.50	$1,040.60