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	$91.59	12.576%	$103.1084	$103.11	$103.10	$103.10
Purchase #2	$138.74	6.387%	$147.6013	$147.60	$147.60	$147.60
Purchase #3	$95.41	12.791%	$107.6139	$107.61	$107.60	$107.60
Purchase #4	$51.98	10.735%	$57.5601	$57.56	$57.55	$57.60
Purchase #5	$209.47	7.564%	$225.3143	$225.31	$225.30	$225.30
Purchase #6	$222.34	4.864%	$233.1546	$233.15	$233.15	$233.20
Purchase #7	$165.79	11.812%	$185.3731	$185.37	$185.35	$185.40
7 purchase totals =	$975.32		$1,059.7257	$1,059.71	$1,059.65	$1,059.80