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	$48.97	3.772%	$50.8171	$50.82	$50.80	$50.80
Purchase #2	$238.83	4.361%	$249.2454	$249.25	$249.25	$249.20
Purchase #3	$68.61	5.503%	$72.3856	$72.39	$72.40	$72.40
Purchase #4	$18.63	8.834%	$20.2758	$20.28	$20.30	$20.30
Purchase #5	$208.34	4.814%	$218.3695	$218.37	$218.35	$218.40
Purchase #6	$85.60	3.663%	$88.7355	$88.74	$88.75	$88.70
Purchase #7	$100.74	11.775%	$112.6021	$112.60	$112.60	$112.60
7 purchase totals =	$769.72		$812.4310	$812.45	$812.45	$812.40