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	$183.50	13.463%	$208.2046	$208.20	$208.20	$208.20
Purchase #2	$205.65	8.139%	$222.3879	$222.39	$222.40	$222.40
Purchase #3	$103.66	11.801%	$115.8929	$115.89	$115.90	$115.90
Purchase #4	$161.50	3.120%	$166.5388	$166.54	$166.55	$166.50
Purchase #5	$150.86	10.533%	$166.7501	$166.75	$166.75	$166.80
Purchase #6	$59.39	13.363%	$67.3263	$67.33	$67.35	$67.30
Purchase #7	$188.34	6.336%	$200.2732	$200.27	$200.25	$200.30
7 purchase totals =	$1,052.90		$1,147.3738	$1,147.37	$1,147.40	$1,147.40