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	$179.79	9.443%	$196.7676	$196.77	$196.75	$196.80
Purchase #2	$81.91	5.691%	$86.5715	$86.57	$86.55	$86.60
Purchase #3	$18.49	6.873%	$19.7608	$19.76	$19.75	$19.80
Purchase #4	$228.74	12.278%	$256.8247	$256.82	$256.80	$256.80
Purchase #5	$247.37	9.241%	$270.2295	$270.23	$270.25	$270.20
Purchase #6	$60.77	4.321%	$63.3959	$63.40	$63.40	$63.40
Purchase #7	$42.26	3.714%	$43.8295	$43.83	$43.85	$43.80
7 purchase totals =	$859.33		$937.3795	$937.38	$937.35	$937.40