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	$179.29	6.660%	$191.2307	$191.23	$191.25	$191.20
Purchase #2	$161.31	4.399%	$168.406	$168.41	$168.40	$168.40
Purchase #3	$218.54	7.236%	$234.3536	$234.35	$234.35	$234.40
Purchase #4	$154.40	6.584%	$164.5657	$164.57	$164.55	$164.60
Purchase #5	$171.90	11.575%	$191.7974	$191.80	$191.80	$191.80
Purchase #6	$49.43	5.257%	$52.0285	$52.03	$52.05	$52.00
Purchase #7	$156.95	12.105%	$175.9488	$175.95	$175.95	$175.90
7 purchase totals =	$1,091.82		$1,178.3307	$1,178.34	$1,178.35	$1,178.30