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	$106.81	5.549%	$112.7369	$112.74	$112.75	$112.70
Purchase #2	$136.33	6.238%	$144.8343	$144.83	$144.85	$144.80
Purchase #3	$128.61	9.868%	$141.3012	$141.30	$141.30	$141.30
Purchase #4	$163.86	5.641%	$173.1033	$173.10	$173.10	$173.10
Purchase #5	$151.45	11.276%	$168.5275	$168.53	$168.55	$168.50
Purchase #6	$6.94	3.312%	$7.1699	$7.17	$7.15	$7.20
Purchase #7	$105.51	7.548%	$113.4739	$113.47	$113.45	$113.50
7 purchase totals =	$799.51		$861.1470	$861.14	$861.15	$861.10