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	$89.46	6.835%	$95.5746	$95.57	$95.55	$95.60
Purchase #2	$102.38	9.789%	$112.402	$112.40	$112.40	$112.40
Purchase #3	$56.37	8.288%	$61.0419	$61.04	$61.05	$61.00
Purchase #4	$47.86	5.522%	$50.5028	$50.50	$50.50	$50.50
Purchase #5	$43.65	3.768%	$45.2947	$45.29	$45.30	$45.30
Purchase #6	$56.49	7.853%	$60.9262	$60.93	$60.95	$60.90
Purchase #7	$70.86	8.852%	$77.1325	$77.13	$77.15	$77.10
7 purchase totals =	$467.07		$502.8747	$502.86	$502.90	$502.80