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	$68.84	13.325%	$78.0129	$78.01	$78.00	$78.00
Purchase #2	$125.40	4.726%	$131.3264	$131.33	$131.35	$131.30
Purchase #3	$136.98	5.111%	$143.981	$143.98	$144.00	$144.00
Purchase #4	$197.78	12.300%	$222.1069	$222.11	$222.10	$222.10
Purchase #5	$136.31	13.601%	$154.8495	$154.85	$154.85	$154.80
Purchase #6	$178.83	7.119%	$191.5609	$191.56	$191.55	$191.60
Purchase #7	$147.84	11.193%	$164.3877	$164.39	$164.40	$164.40
7 purchase totals =	$991.98		$1,086.2253	$1,086.23	$1,086.25	$1,086.20