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	$148.70	3.692%	$154.19	$154.19	$154.20	$154.20
Purchase #2	$56.81	4.654%	$59.4539	$59.45	$59.45	$59.50
Purchase #3	$150.84	12.634%	$169.8971	$169.90	$169.90	$169.90
Purchase #4	$34.46	10.718%	$38.1534	$38.15	$38.15	$38.20
Purchase #5	$28.71	6.459%	$30.5644	$30.56	$30.55	$30.60
Purchase #6	$67.98	4.841%	$71.2709	$71.27	$71.25	$71.30
Purchase #7	$173.69	7.240%	$186.2652	$186.27	$186.25	$186.30
7 purchase totals =	$661.19		$709.7949	$709.79	$709.75	$710.00