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	$163.72	9.336%	$179.0049	$179.00	$179.00	$179.00
Purchase #2	$162.76	3.556%	$168.5477	$168.55	$168.55	$168.50
Purchase #3	$184.33	7.372%	$197.9188	$197.92	$197.90	$197.90
Purchase #4	$140.44	6.859%	$150.0728	$150.07	$150.05	$150.10
Purchase #5	$215.89	4.244%	$225.0524	$225.05	$225.05	$225.10
Purchase #6	$172.45	9.723%	$189.2173	$189.22	$189.20	$189.20
Purchase #7	$40.76	4.519%	$42.6019	$42.60	$42.60	$42.60
7 purchase totals =	$1,080.35		$1,152.4158	$1,152.41	$1,152.35	$1,152.40