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	$40.77	6.799%	$43.542	$43.54	$43.55	$43.50
Purchase #2	$69.41	3.202%	$71.6325	$71.63	$71.65	$71.60
Purchase #3	$155.98	12.721%	$175.8222	$175.82	$175.80	$175.80
Purchase #4	$5.78	8.819%	$6.2897	$6.29	$6.30	$6.30
Purchase #5	$43.41	9.337%	$47.4632	$47.46	$47.45	$47.50
Purchase #6	$62.95	7.363%	$67.585	$67.59	$67.60	$67.60
Purchase #7	$176.76	3.828%	$183.5264	$183.53	$183.55	$183.50
7 purchase totals =	$555.06		$595.8610	$595.86	$595.90	$595.80