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	$13.92	7.280%	$14.9334	$14.93	$14.95	$14.90
Purchase #2	$146.76	11.829%	$164.1202	$164.12	$164.10	$164.10
Purchase #3	$106.84	9.386%	$116.868	$116.87	$116.85	$116.90
Purchase #4	$31.65	5.851%	$33.5018	$33.50	$33.50	$33.50
Purchase #5	$59.38	11.735%	$66.3482	$66.35	$66.35	$66.30
Purchase #6	$77.55	4.151%	$80.7691	$80.77	$80.75	$80.80
Purchase #7	$105.74	12.499%	$118.9564	$118.96	$118.95	$119.00
7 purchase totals =	$541.84		$595.4971	$595.50	$595.45	$595.50