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	$100.31	13.581%	$113.9331	$113.93	$113.95	$113.90
Purchase #2	$180.83	11.303%	$201.2692	$201.27	$201.25	$201.30
Purchase #3	$135.85	13.176%	$153.7496	$153.75	$153.75	$153.70
Purchase #4	$228.34	9.117%	$249.1578	$249.16	$249.15	$249.20
Purchase #5	$89.53	12.570%	$100.7839	$100.78	$100.80	$100.80
Purchase #6	$220.78	10.351%	$243.6329	$243.63	$243.65	$243.60
Purchase #7	$80.72	11.617%	$90.0972	$90.10	$90.10	$90.10
7 purchase totals =	$1,036.36		$1,152.6237	$1,152.62	$1,152.65	$1,152.60