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	$238.52	7.305%	$255.9439	$255.94	$255.95	$255.90
Purchase #2	$58.61	13.185%	$66.3377	$66.34	$66.35	$66.30
Purchase #3	$38.25	4.373%	$39.9227	$39.92	$39.90	$39.90
Purchase #4	$209.54	4.741%	$219.4743	$219.47	$219.45	$219.50
Purchase #5	$140.77	8.247%	$152.3793	$152.38	$152.40	$152.40
Purchase #6	$79.84	8.715%	$86.7981	$86.80	$86.80	$86.80
Purchase #7	$66.92	8.600%	$72.6751	$72.68	$72.70	$72.70
7 purchase totals =	$832.45		$893.5311	$893.53	$893.55	$893.50