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	$118.27	11.515%	$131.8888	$131.89	$131.90	$131.90
Purchase #2	$211.45	4.715%	$221.4199	$221.42	$221.40	$221.40
Purchase #3	$119.92	9.674%	$131.5211	$131.52	$131.50	$131.50
Purchase #4	$178.89	13.270%	$202.6287	$202.63	$202.65	$202.60
Purchase #5	$175.48	13.869%	$199.8173	$199.82	$199.80	$199.80
Purchase #6	$59.43	13.831%	$67.6498	$67.65	$67.65	$67.60
Purchase #7	$103.63	9.687%	$113.6686	$113.67	$113.65	$113.70
7 purchase totals =	$967.07		$1,068.5942	$1,068.60	$1,068.55	$1,068.50