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	$156.54	9.243%	$171.009	$171.01	$171.00	$171.00
Purchase #2	$25.64	9.141%	$27.9838	$27.98	$28.00	$28.00
Purchase #3	$240.37	12.683%	$270.8561	$270.86	$270.85	$270.90
Purchase #4	$182.93	6.440%	$194.7107	$194.71	$194.70	$194.70
Purchase #5	$142.32	11.794%	$159.1052	$159.11	$159.10	$159.10
Purchase #6	$73.25	7.509%	$78.7503	$78.75	$78.75	$78.80
Purchase #7	$102.55	5.773%	$108.4702	$108.47	$108.45	$108.50
7 purchase totals =	$923.60		$1,010.8853	$1,010.89	$1,010.85	$1,011.00