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	$161.93	3.586%	$167.7368	$167.74	$167.75	$167.70
Purchase #2	$87.75	13.386%	$99.4962	$99.50	$99.50	$99.50
Purchase #3	$114.88	4.345%	$119.8715	$119.87	$119.85	$119.90
Purchase #4	$97.41	4.241%	$101.5412	$101.54	$101.55	$101.50
Purchase #5	$223.67	6.455%	$238.1079	$238.11	$238.10	$238.10
Purchase #6	$153.38	5.306%	$161.5183	$161.52	$161.50	$161.50
Purchase #7	$209.38	8.772%	$227.7468	$227.75	$227.75	$227.70
7 purchase totals =	$1,048.40		$1,116.0187	$1,116.03	$1,116.00	$1,115.90