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	$188.56	10.608%	$208.5624	$208.56	$208.55	$208.60
Purchase #2	$145.78	8.817%	$158.6334	$158.63	$158.65	$158.60
Purchase #3	$178.33	5.148%	$187.5104	$187.51	$187.50	$187.50
Purchase #4	$152.61	10.252%	$168.2556	$168.26	$168.25	$168.30
Purchase #5	$202.26	10.715%	$223.9322	$223.93	$223.95	$223.90
Purchase #6	$87.47	4.687%	$91.5697	$91.57	$91.55	$91.60
Purchase #7	$222.37	7.430%	$238.8921	$238.89	$238.90	$238.90
7 purchase totals =	$1,177.38		$1,277.3558	$1,277.35	$1,277.35	$1,277.40