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	$63.33	13.661%	$71.9815	$71.98	$72.00	$72.00
Purchase #2	$78.74	3.286%	$81.3274	$81.33	$81.35	$81.30
Purchase #3	$208.35	10.176%	$229.5517	$229.55	$229.55	$229.60
Purchase #4	$104.76	10.370%	$115.6236	$115.62	$115.60	$115.60
Purchase #5	$168.46	13.317%	$190.8938	$190.89	$190.90	$190.90
Purchase #6	$15.27	7.795%	$16.4603	$16.46	$16.45	$16.50
Purchase #7	$58.85	5.192%	$61.9055	$61.91	$61.90	$61.90
7 purchase totals =	$697.76		$767.7438	$767.74	$767.75	$767.80