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	$173.77	8.197%	$188.0139	$188.01	$188.00	$188.00
Purchase #2	$158.72	6.464%	$168.9797	$168.98	$169.00	$169.00
Purchase #3	$156.46	11.115%	$173.8505	$173.85	$173.85	$173.90
Purchase #4	$85.96	10.708%	$95.1646	$95.16	$95.15	$95.20
Purchase #5	$158.80	9.804%	$174.3688	$174.37	$174.35	$174.40
Purchase #6	$113.45	12.629%	$127.7776	$127.78	$127.80	$127.80
Purchase #7	$107.97	4.355%	$112.6721	$112.67	$112.65	$112.70
7 purchase totals =	$955.13		$1,040.8272	$1,040.82	$1,040.80	$1,041.00