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	$87.69	13.759%	$99.7553	$99.76	$99.75	$99.80
Purchase #2	$110.71	11.201%	$123.1106	$123.11	$123.10	$123.10
Purchase #3	$96.37	5.205%	$101.3861	$101.39	$101.40	$101.40
Purchase #4	$220.35	13.215%	$249.4693	$249.47	$249.45	$249.50
Purchase #5	$102.54	9.312%	$112.0885	$112.09	$112.10	$112.10
Purchase #6	$213.84	3.874%	$222.1242	$222.12	$222.10	$222.10
Purchase #7	$106.88	12.187%	$119.9055	$119.91	$119.90	$119.90
7 purchase totals =	$938.38		$1,027.8395	$1,027.85	$1,027.80	$1,027.90