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	$160.38	5.105%	$168.5674	$168.57	$168.55	$168.60
Purchase #2	$146.92	11.838%	$164.3124	$164.31	$164.30	$164.30
Purchase #3	$89.78	5.299%	$94.5374	$94.54	$94.55	$94.50
Purchase #4	$227.85	13.814%	$259.3252	$259.33	$259.35	$259.30
Purchase #5	$53.40	3.603%	$55.324	$55.32	$55.30	$55.30
Purchase #6	$245.31	3.541%	$253.9964	$254.00	$254.00	$254.00
Purchase #7	$249.26	3.281%	$257.4382	$257.44	$257.45	$257.40
7 purchase totals =	$1,172.90		$1,253.5010	$1,253.51	$1,253.50	$1,253.40