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	$230.52	4.447%	$240.7712	$240.77	$240.75	$240.80
Purchase #2	$201.67	13.574%	$229.0447	$229.04	$229.05	$229.00
Purchase #3	$18.59	13.203%	$21.0444	$21.04	$21.05	$21.00
Purchase #4	$209.64	10.672%	$232.0128	$232.01	$232.00	$232.00
Purchase #5	$77.52	9.146%	$84.61	$84.61	$84.60	$84.60
Purchase #6	$184.30	6.354%	$196.0104	$196.01	$196.00	$196.00
Purchase #7	$95.38	4.585%	$99.7532	$99.75	$99.75	$99.80
7 purchase totals =	$1,017.62		$1,103.2467	$1,103.23	$1,103.20	$1,103.20