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	$12.63	4.210%	$13.1617	$13.16	$13.15	$13.20
Purchase #2	$90.49	3.192%	$93.3784	$93.38	$93.40	$93.40
Purchase #3	$100.83	9.626%	$110.5359	$110.54	$110.55	$110.50
Purchase #4	$91.68	5.279%	$96.5198	$96.52	$96.50	$96.50
Purchase #5	$127.96	3.540%	$132.4898	$132.49	$132.50	$132.50
Purchase #6	$115.56	3.631%	$119.756	$119.76	$119.75	$119.80
Purchase #7	$20.74	3.603%	$21.4873	$21.49	$21.50	$21.50
7 purchase totals =	$559.89		$587.3289	$587.34	$587.35	$587.40