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	$82.63	9.664%	$90.6154	$90.62	$90.60	$90.60
Purchase #2	$218.50	5.749%	$231.0616	$231.06	$231.05	$231.10
Purchase #3	$240.67	3.161%	$248.2776	$248.28	$248.30	$248.30
Purchase #4	$141.53	11.423%	$157.697	$157.70	$157.70	$157.70
Purchase #5	$123.55	12.642%	$139.1692	$139.17	$139.15	$139.20
Purchase #6	$131.98	7.112%	$141.3664	$141.37	$141.35	$141.40
Purchase #7	$75.70	9.499%	$82.8907	$82.89	$82.90	$82.90
7 purchase totals =	$1,014.56		$1,091.0779	$1,091.09	$1,091.05	$1,091.20