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	$116.25	13.775%	$132.2634	$132.26	$132.25	$132.30
Purchase #2	$204.54	3.182%	$211.0485	$211.05	$211.05	$211.00
Purchase #3	$42.89	3.519%	$44.3993	$44.40	$44.40	$44.40
Purchase #4	$150.54	10.286%	$166.0245	$166.02	$166.00	$166.00
Purchase #5	$72.38	8.854%	$78.7885	$78.79	$78.80	$78.80
Purchase #6	$225.44	11.170%	$250.6216	$250.62	$250.60	$250.60
Purchase #7	$209.33	3.612%	$216.891	$216.89	$216.90	$216.90
7 purchase totals =	$1,021.37		$1,100.0368	$1,100.03	$1,100.00	$1,100.00