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	$206.92	8.744%	$225.0131	$225.01	$225.00	$225.00
Purchase #2	$68.94	13.712%	$78.3931	$78.39	$78.40	$78.40
Purchase #3	$82.45	6.183%	$87.5479	$87.55	$87.55	$87.50
Purchase #4	$139.57	8.589%	$151.5577	$151.56	$151.55	$151.60
Purchase #5	$109.58	6.844%	$117.0797	$117.08	$117.10	$117.10
Purchase #6	$102.58	6.851%	$109.6078	$109.61	$109.60	$109.60
Purchase #7	$194.87	11.123%	$216.5454	$216.55	$216.55	$216.50
7 purchase totals =	$904.91		$985.7447	$985.75	$985.75	$985.70