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	$156.67	5.721%	$165.6331	$165.63	$165.65	$165.60
Purchase #2	$52.67	4.239%	$54.9027	$54.90	$54.90	$54.90
Purchase #3	$26.32	5.382%	$27.7365	$27.74	$27.75	$27.70
Purchase #4	$189.92	9.671%	$208.2872	$208.29	$208.30	$208.30
Purchase #5	$124.53	5.808%	$131.7627	$131.76	$131.75	$131.80
Purchase #6	$233.79	5.865%	$247.5018	$247.50	$247.50	$247.50
Purchase #7	$126.37	4.204%	$131.6826	$131.68	$131.70	$131.70
7 purchase totals =	$910.27		$967.5066	$967.50	$967.55	$967.50