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	$126.70	3.618%	$131.284	$131.28	$131.30	$131.30
Purchase #2	$72.84	7.257%	$78.126	$78.13	$78.15	$78.10
Purchase #3	$139.27	5.578%	$147.0385	$147.04	$147.05	$147.00
Purchase #4	$159.71	5.167%	$167.9622	$167.96	$167.95	$168.00
Purchase #5	$131.50	8.612%	$142.8248	$142.82	$142.80	$142.80
Purchase #6	$249.40	10.373%	$275.2703	$275.27	$275.25	$275.30
Purchase #7	$77.42	10.670%	$85.6807	$85.68	$85.70	$85.70
7 purchase totals =	$956.84		$1,028.1865	$1,028.18	$1,028.20	$1,028.20