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	$82.52	12.841%	$93.1164	$93.12	$93.10	$93.10
Purchase #2	$239.90	10.543%	$265.1927	$265.19	$265.20	$265.20
Purchase #3	$29.94	7.250%	$32.1107	$32.11	$32.10	$32.10
Purchase #4	$30.66	3.105%	$31.612	$31.61	$31.60	$31.60
Purchase #5	$232.90	12.234%	$261.393	$261.39	$261.40	$261.40
Purchase #6	$246.30	10.582%	$272.3635	$272.36	$272.35	$272.40
Purchase #7	$160.85	4.308%	$167.7794	$167.78	$167.80	$167.80
7 purchase totals =	$1,023.07		$1,123.5677	$1,123.56	$1,123.55	$1,123.60