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	$112.64	9.179%	$122.9792	$122.98	$123.00	$123.00
Purchase #2	$43.61	9.667%	$47.8258	$47.83	$47.85	$47.80
Purchase #3	$175.71	13.228%	$198.9529	$198.95	$198.95	$199.00
Purchase #4	$244.49	10.159%	$269.3277	$269.33	$269.35	$269.30
Purchase #5	$61.31	9.520%	$67.1467	$67.15	$67.15	$67.10
Purchase #6	$136.37	10.465%	$150.6411	$150.64	$150.65	$150.60
Purchase #7	$183.72	13.467%	$208.4616	$208.46	$208.45	$208.50
7 purchase totals =	$957.85		$1,065.3350	$1,065.34	$1,065.40	$1,065.30