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	$206.78	11.124%	$229.7822	$229.78	$229.80	$229.80
Purchase #2	$51.63	7.238%	$55.367	$55.37	$55.35	$55.40
Purchase #3	$129.45	5.544%	$136.6267	$136.63	$136.65	$136.60
Purchase #4	$191.30	4.655%	$200.205	$200.21	$200.20	$200.20
Purchase #5	$216.90	4.420%	$226.487	$226.49	$226.50	$226.50
Purchase #6	$80.54	11.661%	$89.9318	$89.93	$89.95	$89.90
Purchase #7	$182.27	9.351%	$199.3141	$199.31	$199.30	$199.30
7 purchase totals =	$1,058.87		$1,137.7138	$1,137.72	$1,137.75	$1,137.70