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	$55.72	6.697%	$59.4516	$59.45	$59.45	$59.50
Purchase #2	$38.86	3.498%	$40.2193	$40.22	$40.20	$40.20
Purchase #3	$203.29	5.456%	$214.3815	$214.38	$214.40	$214.40
Purchase #4	$196.71	12.287%	$220.8798	$220.88	$220.90	$220.90
Purchase #5	$115.28	12.373%	$129.5436	$129.54	$129.55	$129.50
Purchase #6	$159.97	5.580%	$168.8963	$168.90	$168.90	$168.90
Purchase #7	$59.43	4.636%	$62.1852	$62.19	$62.20	$62.20
7 purchase totals =	$829.26		$895.5573	$895.56	$895.60	$895.60