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	$188.27	11.817%	$210.5179	$210.52	$210.50	$210.50
Purchase #2	$197.33	8.112%	$213.3374	$213.34	$213.35	$213.30
Purchase #3	$101.43	8.329%	$109.8781	$109.88	$109.90	$109.90
Purchase #4	$147.57	13.438%	$167.4005	$167.40	$167.40	$167.40
Purchase #5	$59.43	10.418%	$65.6214	$65.62	$65.60	$65.60
Purchase #6	$51.86	5.786%	$54.8606	$54.86	$54.85	$54.90
Purchase #7	$233.62	13.565%	$265.3106	$265.31	$265.30	$265.30
7 purchase totals =	$979.51		$1,086.9265	$1,086.93	$1,086.90	$1,086.90