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	$216.92	9.393%	$237.2953	$237.30	$237.30	$237.30
Purchase #2	$107.32	9.757%	$117.7912	$117.79	$117.80	$117.80
Purchase #3	$75.69	9.113%	$82.5876	$82.59	$82.60	$82.60
Purchase #4	$109.43	5.425%	$115.3666	$115.37	$115.35	$115.40
Purchase #5	$81.76	12.743%	$92.1787	$92.18	$92.20	$92.20
Purchase #6	$118.82	4.218%	$123.8318	$123.83	$123.85	$123.80
Purchase #7	$72.82	7.722%	$78.4432	$78.44	$78.45	$78.40
7 purchase totals =	$782.76		$847.4944	$847.50	$847.55	$847.50