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	$212.45	12.677%	$239.3823	$239.38	$239.40	$239.40
Purchase #2	$158.91	4.397%	$165.8973	$165.90	$165.90	$165.90
Purchase #3	$144.44	4.490%	$150.9254	$150.93	$150.95	$150.90
Purchase #4	$43.60	13.827%	$49.6286	$49.63	$49.65	$49.60
Purchase #5	$53.40	5.661%	$56.423	$56.42	$56.40	$56.40
Purchase #6	$175.52	10.813%	$194.499	$194.50	$194.50	$194.50
Purchase #7	$215.51	8.503%	$233.8348	$233.83	$233.85	$233.80
7 purchase totals =	$1,003.83		$1,090.5904	$1,090.59	$1,090.65	$1,090.50