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	$85.85	11.551%	$95.7665	$95.77	$95.75	$95.80
Purchase #2	$156.52	6.506%	$166.7032	$166.70	$166.70	$166.70
Purchase #3	$192.94	11.180%	$214.5107	$214.51	$214.50	$214.50
Purchase #4	$155.85	6.472%	$165.9366	$165.94	$165.95	$165.90
Purchase #5	$184.67	8.798%	$200.9173	$200.92	$200.90	$200.90
Purchase #6	$174.31	7.459%	$187.3118	$187.31	$187.30	$187.30
Purchase #7	$56.70	4.107%	$59.0287	$59.03	$59.05	$59.00
7 purchase totals =	$1,006.84		$1,090.1748	$1,090.18	$1,090.15	$1,090.10