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	$183.55	7.423%	$197.1749	$197.17	$197.15	$197.20
Purchase #2	$135.59	4.370%	$141.5153	$141.52	$141.50	$141.50
Purchase #3	$106.90	12.351%	$120.1032	$120.10	$120.10	$120.10
Purchase #4	$102.55	9.511%	$112.3035	$112.30	$112.30	$112.30
Purchase #5	$86.39	5.210%	$90.8909	$90.89	$90.90	$90.90
Purchase #6	$142.98	6.693%	$152.5497	$152.55	$152.55	$152.50
Purchase #7	$137.43	9.327%	$150.2481	$150.25	$150.25	$150.20
7 purchase totals =	$895.39		$964.7856	$964.78	$964.75	$964.70