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	$105.67	7.474%	$113.5678	$113.57	$113.55	$113.60
Purchase #2	$60.30	5.334%	$63.5164	$63.52	$63.50	$63.50
Purchase #3	$40.78	12.516%	$45.884	$45.88	$45.90	$45.90
Purchase #4	$139.62	9.429%	$152.7848	$152.78	$152.80	$152.80
Purchase #5	$139.74	13.588%	$158.7279	$158.73	$158.75	$158.70
Purchase #6	$129.42	7.686%	$139.3672	$139.37	$139.35	$139.40
Purchase #7	$90.81	8.535%	$98.5606	$98.56	$98.55	$98.60
7 purchase totals =	$706.34		$772.4087	$772.41	$772.40	$772.50