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	$176.97	9.521%	$193.8193	$193.82	$193.80	$193.80
Purchase #2	$39.56	3.668%	$41.0111	$41.01	$41.00	$41.00
Purchase #3	$73.76	6.580%	$78.6134	$78.61	$78.60	$78.60
Purchase #4	$26.68	7.597%	$28.7069	$28.71	$28.70	$28.70
Purchase #5	$158.36	4.841%	$166.0262	$166.03	$166.05	$166.00
Purchase #6	$83.94	7.741%	$90.4378	$90.44	$90.45	$90.40
Purchase #7	$176.31	6.641%	$188.0187	$188.02	$188.00	$188.00
7 purchase totals =	$735.58		$786.6334	$786.64	$786.60	$786.50