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	$165.86	5.314%	$174.6738	$174.67	$174.65	$174.70
Purchase #2	$101.76	11.788%	$113.7555	$113.76	$113.75	$113.80
Purchase #3	$206.69	11.739%	$230.9533	$230.95	$230.95	$231.00
Purchase #4	$238.37	7.477%	$256.1929	$256.19	$256.20	$256.20
Purchase #5	$130.33	8.601%	$141.5397	$141.54	$141.55	$141.50
Purchase #6	$54.52	5.857%	$57.7132	$57.71	$57.70	$57.70
Purchase #7	$33.84	9.665%	$37.1106	$37.11	$37.10	$37.10
7 purchase totals =	$931.37		$1,011.9390	$1,011.93	$1,011.90	$1,012.00