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	$35.51	4.496%	$37.1065	$37.11	$37.10	$37.10
Purchase #2	$78.88	8.444%	$85.5406	$85.54	$85.55	$85.50
Purchase #3	$63.32	8.420%	$68.6515	$68.65	$68.65	$68.70
Purchase #4	$153.33	8.565%	$166.4627	$166.46	$166.45	$166.50
Purchase #5	$7.78	13.837%	$8.8565	$8.86	$8.85	$8.90
Purchase #6	$222.57	4.187%	$231.889	$231.89	$231.90	$231.90
Purchase #7	$108.54	4.800%	$113.7499	$113.75	$113.75	$113.70
7 purchase totals =	$669.93		$712.2567	$712.26	$712.25	$712.30