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	$50.30	3.399%	$52.0097	$52.01	$52.00	$52.00
Purchase #2	$38.49	13.288%	$43.6046	$43.60	$43.60	$43.60
Purchase #3	$222.39	9.704%	$243.9707	$243.97	$243.95	$244.00
Purchase #4	$242.99	6.824%	$259.5716	$259.57	$259.55	$259.60
Purchase #5	$222.85	3.508%	$230.6676	$230.67	$230.65	$230.70
Purchase #6	$50.36	8.294%	$54.5369	$54.54	$54.55	$54.50
Purchase #7	$38.45	10.769%	$42.5907	$42.59	$42.60	$42.60
7 purchase totals =	$865.83		$926.9518	$926.95	$926.90	$927.00