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	$175.31	12.111%	$196.5418	$196.54	$196.55	$196.50
Purchase #2	$237.51	13.389%	$269.3102	$269.31	$269.30	$269.30
Purchase #3	$132.50	4.139%	$137.9842	$137.98	$138.00	$138.00
Purchase #4	$115.25	4.774%	$120.752	$120.75	$120.75	$120.80
Purchase #5	$174.61	13.676%	$198.4897	$198.49	$198.50	$198.50
Purchase #6	$193.93	5.782%	$205.143	$205.14	$205.15	$205.10
Purchase #7	$90.90	4.358%	$94.8614	$94.86	$94.85	$94.90
7 purchase totals =	$1,120.01		$1,223.0823	$1,223.07	$1,223.10	$1,223.10