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	$140.90	8.432%	$152.7807	$152.78	$152.80	$152.80
Purchase #2	$6.79	5.378%	$7.1552	$7.16	$7.15	$7.20
Purchase #3	$144.29	13.873%	$164.3074	$164.31	$164.30	$164.30
Purchase #4	$85.84	4.177%	$89.4255	$89.43	$89.45	$89.40
Purchase #5	$241.71	7.750%	$260.4425	$260.44	$260.45	$260.40
Purchase #6	$163.38	3.420%	$168.9676	$168.97	$168.95	$169.00
Purchase #7	$147.81	5.839%	$156.4406	$156.44	$156.45	$156.40
7 purchase totals =	$930.72		$999.5195	$999.53	$999.55	$999.50