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	$105.54	4.102%	$109.8693	$109.87	$109.85	$109.90
Purchase #2	$146.69	3.853%	$152.342	$152.34	$152.35	$152.30
Purchase #3	$164.88	8.150%	$178.3177	$178.32	$178.30	$178.30
Purchase #4	$63.25	3.226%	$65.2904	$65.29	$65.30	$65.30
Purchase #5	$36.33	5.641%	$38.3794	$38.38	$38.40	$38.40
Purchase #6	$86.77	4.791%	$90.9272	$90.93	$90.95	$90.90
Purchase #7	$30.38	12.257%	$34.1037	$34.10	$34.10	$34.10
7 purchase totals =	$633.84		$669.2297	$669.23	$669.25	$669.20