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	$184.71	3.278%	$190.7648	$190.76	$190.75	$190.80
Purchase #2	$246.72	13.686%	$280.4861	$280.49	$280.50	$280.50
Purchase #3	$26.86	5.757%	$28.4063	$28.41	$28.40	$28.40
Purchase #4	$171.50	5.835%	$181.507	$181.51	$181.50	$181.50
Purchase #5	$245.78	10.210%	$270.8741	$270.87	$270.85	$270.90
Purchase #6	$13.65	3.669%	$14.1508	$14.15	$14.15	$14.20
Purchase #7	$165.46	6.116%	$175.5795	$175.58	$175.60	$175.60
7 purchase totals =	$1,054.68		$1,141.7686	$1,141.77	$1,141.75	$1,141.90