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	$43.46	9.264%	$47.4861	$47.49	$47.50	$47.50
Purchase #2	$128.30	12.416%	$144.2297	$144.23	$144.25	$144.20
Purchase #3	$159.41	12.809%	$179.8288	$179.83	$179.85	$179.80
Purchase #4	$182.78	7.460%	$196.4154	$196.42	$196.40	$196.40
Purchase #5	$194.58	3.651%	$201.6841	$201.68	$201.70	$201.70
Purchase #6	$20.69	4.713%	$21.6651	$21.67	$21.65	$21.70
Purchase #7	$78.52	10.576%	$86.8243	$86.82	$86.80	$86.80
7 purchase totals =	$807.74		$878.1335	$878.14	$878.15	$878.10