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	$208.90	3.336%	$215.8689	$215.87	$215.85	$215.90
Purchase #2	$216.76	4.206%	$225.8769	$225.88	$225.90	$225.90
Purchase #3	$162.38	6.192%	$172.4346	$172.43	$172.45	$172.40
Purchase #4	$222.88	9.232%	$243.4563	$243.46	$243.45	$243.50
Purchase #5	$89.70	3.401%	$92.7507	$92.75	$92.75	$92.80
Purchase #6	$128.68	5.618%	$135.9092	$135.91	$135.90	$135.90
Purchase #7	$169.60	9.197%	$185.1981	$185.20	$185.20	$185.20
7 purchase totals =	$1,198.90		$1,271.4947	$1,271.50	$1,271.50	$1,271.60