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	$34.69	7.645%	$37.3421	$37.34	$37.35	$37.30
Purchase #2	$168.90	10.494%	$186.6244	$186.62	$186.60	$186.60
Purchase #3	$207.45	7.558%	$223.1291	$223.13	$223.15	$223.10
Purchase #4	$55.27	10.729%	$61.1999	$61.20	$61.20	$61.20
Purchase #5	$149.43	9.554%	$163.7065	$163.71	$163.70	$163.70
Purchase #6	$194.50	10.133%	$214.2087	$214.21	$214.20	$214.20
Purchase #7	$119.34	6.738%	$127.3811	$127.38	$127.40	$127.40
7 purchase totals =	$929.58		$1,013.5918	$1,013.59	$1,013.60	$1,013.50