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	$238.92	7.522%	$256.8916	$256.89	$256.90	$256.90
Purchase #2	$38.81	10.622%	$42.9324	$42.93	$42.95	$42.90
Purchase #3	$23.40	3.677%	$24.2604	$24.26	$24.25	$24.30
Purchase #4	$239.82	12.212%	$269.1068	$269.11	$269.10	$269.10
Purchase #5	$182.77	3.420%	$189.0207	$189.02	$189.00	$189.00
Purchase #6	$41.78	10.843%	$46.3102	$46.31	$46.30	$46.30
Purchase #7	$240.72	11.325%	$267.9815	$267.98	$268.00	$268.00
7 purchase totals =	$1,006.22		$1,096.5036	$1,096.50	$1,096.50	$1,096.50