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	$167.95	7.670%	$180.8318	$180.83	$180.85	$180.80
Purchase #2	$37.86	6.523%	$40.3296	$40.33	$40.35	$40.30
Purchase #3	$147.94	11.366%	$164.7549	$164.75	$164.75	$164.80
Purchase #4	$201.71	11.857%	$225.6268	$225.63	$225.65	$225.60
Purchase #5	$39.92	3.828%	$41.4481	$41.45	$41.45	$41.40
Purchase #6	$51.56	6.162%	$54.7371	$54.74	$54.75	$54.70
Purchase #7	$190.84	11.779%	$213.319	$213.32	$213.30	$213.30
7 purchase totals =	$837.78		$921.0473	$921.05	$921.10	$920.90