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	$201.37	6.148%	$213.7502	$213.75	$213.75	$213.80
Purchase #2	$209.47	11.327%	$233.1967	$233.20	$233.20	$233.20
Purchase #3	$199.89	8.402%	$216.6848	$216.68	$216.70	$216.70
Purchase #4	$170.74	8.509%	$185.2683	$185.27	$185.25	$185.30
Purchase #5	$28.87	9.681%	$31.6649	$31.66	$31.65	$31.70
Purchase #6	$130.82	8.127%	$141.4517	$141.45	$141.45	$141.50
Purchase #7	$70.80	11.337%	$78.8266	$78.83	$78.85	$78.80
7 purchase totals =	$1,011.96		$1,100.8432	$1,100.84	$1,100.85	$1,101.00