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	$182.45	9.514%	$199.8083	$199.81	$199.80	$199.80
Purchase #2	$180.27	7.808%	$194.3455	$194.35	$194.35	$194.30
Purchase #3	$147.78	5.821%	$156.3823	$156.38	$156.40	$156.40
Purchase #4	$160.84	11.601%	$179.499	$179.50	$179.50	$179.50
Purchase #5	$195.92	13.431%	$222.234	$222.23	$222.25	$222.20
Purchase #6	$62.83	12.722%	$70.8232	$70.82	$70.80	$70.80
Purchase #7	$185.94	10.589%	$205.6292	$205.63	$205.65	$205.60
7 purchase totals =	$1,116.03		$1,228.7215	$1,228.72	$1,228.75	$1,228.60