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	$107.42	9.802%	$117.9493	$117.95	$117.95	$117.90
Purchase #2	$76.58	6.261%	$81.3747	$81.37	$81.35	$81.40
Purchase #3	$69.44	13.477%	$78.7984	$78.80	$78.80	$78.80
Purchase #4	$204.64	13.613%	$232.4976	$232.50	$232.50	$232.50
Purchase #5	$225.36	4.663%	$235.8685	$235.87	$235.85	$235.90
Purchase #6	$48.78	11.540%	$54.4092	$54.41	$54.40	$54.40
Purchase #7	$38.34	13.263%	$43.425	$43.43	$43.45	$43.40
7 purchase totals =	$770.56		$844.3227	$844.33	$844.30	$844.30