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	$237.62	3.655%	$246.305	$246.31	$246.30	$246.30
Purchase #2	$31.29	8.859%	$34.062	$34.06	$34.05	$34.10
Purchase #3	$106.28	6.112%	$112.7758	$112.78	$112.80	$112.80
Purchase #4	$36.92	3.596%	$38.2476	$38.25	$38.25	$38.20
Purchase #5	$118.56	7.846%	$127.8622	$127.86	$127.85	$127.90
Purchase #6	$89.43	12.309%	$100.4379	$100.44	$100.45	$100.40
Purchase #7	$31.89	5.334%	$33.591	$33.59	$33.60	$33.60
7 purchase totals =	$651.99		$693.2815	$693.29	$693.30	$693.30