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	$74.89	4.555%	$78.3012	$78.30	$78.30	$78.30
Purchase #2	$107.91	12.646%	$121.5563	$121.56	$121.55	$121.60
Purchase #3	$171.33	12.362%	$192.5098	$192.51	$192.50	$192.50
Purchase #4	$248.77	12.624%	$280.1747	$280.17	$280.15	$280.20
Purchase #5	$231.61	4.269%	$241.4974	$241.50	$241.50	$241.50
Purchase #6	$88.37	5.676%	$93.3859	$93.39	$93.40	$93.40
Purchase #7	$98.28	12.662%	$110.7242	$110.72	$110.70	$110.70
7 purchase totals =	$1,021.16		$1,118.1495	$1,118.15	$1,118.10	$1,118.20