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	$191.46	4.868%	$200.7803	$200.78	$200.80	$200.80
Purchase #2	$167.80	10.710%	$185.7714	$185.77	$185.75	$185.80
Purchase #3	$71.27	12.542%	$80.2087	$80.21	$80.20	$80.20
Purchase #4	$224.60	12.405%	$252.4616	$252.46	$252.45	$252.50
Purchase #5	$40.51	10.844%	$44.9029	$44.90	$44.90	$44.90
Purchase #6	$50.79	5.152%	$53.4067	$53.41	$53.40	$53.40
Purchase #7	$218.45	11.568%	$243.7203	$243.72	$243.70	$243.70
7 purchase totals =	$964.88		$1,061.2519	$1,061.25	$1,061.20	$1,061.30