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	$121.61	4.742%	$127.3767	$127.38	$127.40	$127.40
Purchase #2	$12.31	7.456%	$13.2278	$13.23	$13.25	$13.20
Purchase #3	$179.85	5.205%	$189.2112	$189.21	$189.20	$189.20
Purchase #4	$212.70	7.342%	$228.3164	$228.32	$228.30	$228.30
Purchase #5	$89.42	12.228%	$100.3543	$100.35	$100.35	$100.40
Purchase #6	$115.83	9.780%	$127.1582	$127.16	$127.15	$127.20
Purchase #7	$161.59	8.803%	$175.8148	$175.81	$175.80	$175.80
7 purchase totals =	$893.31		$961.4594	$961.46	$961.45	$961.50