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	$82.50	4.776%	$86.4402	$86.44	$86.45	$86.40
Purchase #2	$88.69	11.708%	$99.0738	$99.07	$99.05	$99.10
Purchase #3	$17.28	6.137%	$18.3405	$18.34	$18.35	$18.30
Purchase #4	$73.83	11.458%	$82.2894	$82.29	$82.30	$82.30
Purchase #5	$6.61	6.724%	$7.0545	$7.05	$7.05	$7.10
Purchase #6	$60.60	12.598%	$68.2344	$68.23	$68.25	$68.20
Purchase #7	$170.86	11.124%	$189.8665	$189.87	$189.85	$189.90
7 purchase totals =	$500.37		$551.2993	$551.29	$551.30	$551.30