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	$173.55	10.314%	$191.4499	$191.45	$191.45	$191.40
Purchase #2	$151.43	10.713%	$167.6527	$167.65	$167.65	$167.70
Purchase #3	$25.38	6.498%	$27.0292	$27.03	$27.05	$27.00
Purchase #4	$5.94	6.509%	$6.3266	$6.33	$6.35	$6.30
Purchase #5	$61.98	6.403%	$65.9486	$65.95	$65.95	$65.90
Purchase #6	$100.43	4.175%	$104.623	$104.62	$104.60	$104.60
Purchase #7	$185.48	13.342%	$210.2267	$210.23	$210.25	$210.20
7 purchase totals =	$704.19		$773.2567	$773.26	$773.30	$773.10