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	$175.34	9.488%	$191.9763	$191.98	$192.00	$192.00
Purchase #2	$62.61	3.583%	$64.8533	$64.85	$64.85	$64.90
Purchase #3	$158.47	4.612%	$165.7786	$165.78	$165.80	$165.80
Purchase #4	$42.75	7.264%	$45.8554	$45.86	$45.85	$45.90
Purchase #5	$133.48	6.864%	$142.6421	$142.64	$142.65	$142.60
Purchase #6	$44.96	13.592%	$51.071	$51.07	$51.05	$51.10
Purchase #7	$243.94	12.202%	$273.7056	$273.71	$273.70	$273.70
7 purchase totals =	$861.55		$935.8823	$935.89	$935.90	$936.00