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	$213.48	9.305%	$233.3443	$233.34	$233.35	$233.30
Purchase #2	$226.50	9.751%	$248.586	$248.59	$248.60	$248.60
Purchase #3	$184.52	9.139%	$201.3833	$201.38	$201.40	$201.40
Purchase #4	$30.84	8.314%	$33.404	$33.40	$33.40	$33.40
Purchase #5	$32.54	6.126%	$34.5334	$34.53	$34.55	$34.50
Purchase #6	$205.60	11.319%	$228.8719	$228.87	$228.85	$228.90
Purchase #7	$109.61	9.789%	$120.3397	$120.34	$120.35	$120.30
7 purchase totals =	$1,003.09		$1,100.4626	$1,100.45	$1,100.50	$1,100.40