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	$137.36	7.851%	$148.1441	$148.14	$148.15	$148.10
Purchase #2	$231.28	9.835%	$254.0264	$254.03	$254.05	$254.00
Purchase #3	$123.52	12.641%	$139.1342	$139.13	$139.15	$139.10
Purchase #4	$100.40	8.622%	$109.0565	$109.06	$109.05	$109.10
Purchase #5	$176.42	8.236%	$190.95	$190.95	$190.95	$191.00
Purchase #6	$197.96	9.407%	$216.5821	$216.58	$216.60	$216.60
Purchase #7	$135.33	5.331%	$142.5444	$142.54	$142.55	$142.50
7 purchase totals =	$1,102.27		$1,200.4377	$1,200.43	$1,200.50	$1,200.40