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	$173.99	12.681%	$196.0537	$196.05	$196.05	$196.10
Purchase #2	$72.51	11.569%	$80.8987	$80.90	$80.90	$80.90
Purchase #3	$63.30	5.351%	$66.6872	$66.69	$66.70	$66.70
Purchase #4	$240.25	8.728%	$261.219	$261.22	$261.20	$261.20
Purchase #5	$118.99	6.766%	$127.0409	$127.04	$127.05	$127.00
Purchase #6	$125.90	13.222%	$142.5465	$142.55	$142.55	$142.50
Purchase #7	$89.92	11.213%	$100.0027	$100.00	$100.00	$100.00
7 purchase totals =	$884.86		$974.4487	$974.45	$974.45	$974.40