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	$152.38	8.670%	$165.5913	$165.59	$165.60	$165.60
Purchase #2	$77.89	8.239%	$84.3074	$84.31	$84.30	$84.30
Purchase #3	$145.84	9.367%	$159.5008	$159.50	$159.50	$159.50
Purchase #4	$99.93	4.325%	$104.252	$104.25	$104.25	$104.30
Purchase #5	$184.64	7.170%	$197.8787	$197.88	$197.90	$197.90
Purchase #6	$175.58	8.524%	$190.5464	$190.55	$190.55	$190.50
Purchase #7	$164.63	10.789%	$182.3919	$182.39	$182.40	$182.40
7 purchase totals =	$1,000.89		$1,084.4685	$1,084.47	$1,084.50	$1,084.50