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	$209.73	12.199%	$235.315	$235.32	$235.30	$235.30
Purchase #2	$118.37	7.481%	$127.2253	$127.23	$127.25	$127.20
Purchase #3	$233.60	9.552%	$255.9135	$255.91	$255.90	$255.90
Purchase #4	$74.46	5.584%	$78.6178	$78.62	$78.60	$78.60
Purchase #5	$118.43	6.561%	$126.2002	$126.20	$126.20	$126.20
Purchase #6	$178.82	13.460%	$202.8892	$202.89	$202.90	$202.90
Purchase #7	$92.40	7.338%	$99.1803	$99.18	$99.20	$99.20
7 purchase totals =	$1,025.81		$1,125.3413	$1,125.35	$1,125.35	$1,125.30