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	$173.88	10.129%	$191.4923	$191.49	$191.50	$191.50
Purchase #2	$85.89	4.667%	$89.8985	$89.90	$89.90	$89.90
Purchase #3	$209.42	3.514%	$216.779	$216.78	$216.80	$216.80
Purchase #4	$167.32	12.432%	$188.1212	$188.12	$188.10	$188.10
Purchase #5	$8.70	10.421%	$9.6066	$9.61	$9.60	$9.60
Purchase #6	$245.83	3.868%	$255.3387	$255.34	$255.35	$255.30
Purchase #7	$214.91	6.447%	$228.7652	$228.77	$228.75	$228.80
7 purchase totals =	$1,105.95		$1,180.0015	$1,180.01	$1,180.00	$1,180.00