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	$191.35	4.808%	$200.5501	$200.55	$200.55	$200.60
Purchase #2	$70.26	10.388%	$77.5586	$77.56	$77.55	$77.60
Purchase #3	$140.32	13.588%	$159.3867	$159.39	$159.40	$159.40
Purchase #4	$225.63	9.605%	$247.3018	$247.30	$247.30	$247.30
Purchase #5	$148.62	9.389%	$162.5739	$162.57	$162.55	$162.60
Purchase #6	$103.26	4.148%	$107.5432	$107.54	$107.55	$107.50
Purchase #7	$79.64	3.650%	$82.5469	$82.55	$82.55	$82.50
7 purchase totals =	$959.08		$1,037.4612	$1,037.46	$1,037.45	$1,037.50