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	$128.64	9.851%	$141.3123	$141.31	$141.30	$141.30
Purchase #2	$248.67	3.808%	$258.1394	$258.14	$258.15	$258.10
Purchase #3	$137.33	9.816%	$150.8103	$150.81	$150.80	$150.80
Purchase #4	$50.99	12.676%	$57.4535	$57.45	$57.45	$57.50
Purchase #5	$48.72	9.265%	$53.2339	$53.23	$53.25	$53.20
Purchase #6	$83.45	10.632%	$92.3224	$92.32	$92.30	$92.30
Purchase #7	$247.37	4.856%	$259.3823	$259.38	$259.40	$259.40
7 purchase totals =	$945.17		$1,012.6541	$1,012.64	$1,012.65	$1,012.60