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	$125.84	10.545%	$139.1098	$139.11	$139.10	$139.10
Purchase #2	$53.81	4.298%	$56.1228	$56.12	$56.10	$56.10
Purchase #3	$40.55	3.676%	$42.0406	$42.04	$42.05	$42.00
Purchase #4	$29.55	13.518%	$33.5446	$33.54	$33.55	$33.50
Purchase #5	$158.82	9.581%	$174.0365	$174.04	$174.05	$174.00
Purchase #6	$120.86	9.833%	$132.7442	$132.74	$132.75	$132.70
Purchase #7	$160.81	3.560%	$166.5348	$166.53	$166.55	$166.50
7 purchase totals =	$690.24		$744.1333	$744.12	$744.15	$743.90