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	$156.83	4.765%	$164.3029	$164.30	$164.30	$164.30
Purchase #2	$200.90	11.126%	$223.2521	$223.25	$223.25	$223.30
Purchase #3	$82.88	8.418%	$89.8568	$89.86	$89.85	$89.90
Purchase #4	$209.71	5.359%	$220.9484	$220.95	$220.95	$220.90
Purchase #5	$80.57	8.736%	$87.6086	$87.61	$87.60	$87.60
Purchase #6	$114.96	7.624%	$123.7246	$123.72	$123.70	$123.70
Purchase #7	$170.85	3.324%	$176.5291	$176.53	$176.55	$176.50
7 purchase totals =	$1,016.70		$1,086.2225	$1,086.22	$1,086.20	$1,086.20