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	$210.54	9.750%	$231.0677	$231.07	$231.05	$231.10
Purchase #2	$151.35	10.266%	$166.8876	$166.89	$166.90	$166.90
Purchase #3	$189.25	11.855%	$211.6856	$211.69	$211.70	$211.70
Purchase #4	$180.46	5.179%	$189.806	$189.81	$189.80	$189.80
Purchase #5	$83.73	6.534%	$89.2009	$89.20	$89.20	$89.20
Purchase #6	$92.38	13.636%	$104.9769	$104.98	$105.00	$105.00
Purchase #7	$37.94	10.738%	$42.014	$42.01	$42.00	$42.00
7 purchase totals =	$945.65		$1,035.6387	$1,035.65	$1,035.65	$1,035.70