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	$250.90	10.382%	$276.9484	$276.95	$276.95	$276.90
Purchase #2	$91.38	13.802%	$103.9923	$103.99	$104.00	$104.00
Purchase #3	$20.91	3.602%	$21.6632	$21.66	$21.65	$21.70
Purchase #4	$175.64	13.809%	$199.8941	$199.89	$199.90	$199.90
Purchase #5	$156.89	6.132%	$166.5105	$166.51	$166.50	$166.50
Purchase #6	$207.81	3.166%	$214.3893	$214.39	$214.40	$214.40
Purchase #7	$153.73	7.294%	$164.9431	$164.94	$164.95	$164.90
7 purchase totals =	$1,057.26		$1,148.3409	$1,148.33	$1,148.35	$1,148.30