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	$231.72	12.781%	$261.3361	$261.34	$261.35	$261.30
Purchase #2	$151.90	13.627%	$172.5994	$172.60	$172.60	$172.60
Purchase #3	$59.50	6.722%	$63.4996	$63.50	$63.50	$63.50
Purchase #4	$62.47	6.525%	$66.5462	$66.55	$66.55	$66.50
Purchase #5	$101.92	7.498%	$109.562	$109.56	$109.55	$109.60
Purchase #6	$188.30	4.815%	$197.3666	$197.37	$197.35	$197.40
Purchase #7	$170.76	12.772%	$192.5695	$192.57	$192.55	$192.60
7 purchase totals =	$966.57		$1,063.4794	$1,063.49	$1,063.45	$1,063.50