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	$10.45	9.230%	$11.4145	$11.41	$11.40	$11.40
Purchase #2	$75.90	13.778%	$86.3575	$86.36	$86.35	$86.40
Purchase #3	$215.47	3.744%	$223.5372	$223.54	$223.55	$223.50
Purchase #4	$152.40	8.621%	$165.5384	$165.54	$165.55	$165.50
Purchase #5	$178.26	10.144%	$196.3427	$196.34	$196.35	$196.30
Purchase #6	$193.73	7.434%	$208.1319	$208.13	$208.15	$208.10
Purchase #7	$155.92	5.680%	$164.7763	$164.78	$164.80	$164.80
7 purchase totals =	$982.13		$1,056.0985	$1,056.10	$1,056.15	$1,056.00