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	$177.54	13.571%	$201.634	$201.63	$201.65	$201.60
Purchase #2	$127.82	4.799%	$133.9541	$133.95	$133.95	$134.00
Purchase #3	$129.54	9.305%	$141.5937	$141.59	$141.60	$141.60
Purchase #4	$24.49	5.199%	$25.7632	$25.76	$25.75	$25.80
Purchase #5	$67.54	7.460%	$72.5785	$72.58	$72.60	$72.60
Purchase #6	$215.52	3.242%	$222.5072	$222.51	$222.50	$222.50
Purchase #7	$51.56	11.240%	$57.3553	$57.36	$57.35	$57.40
7 purchase totals =	$794.01		$855.3860	$855.38	$855.40	$855.50