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	$71.65	9.372%	$78.365	$78.37	$78.35	$78.40
Purchase #2	$28.83	6.631%	$30.7417	$30.74	$30.75	$30.70
Purchase #3	$72.84	13.334%	$82.5525	$82.55	$82.55	$82.60
Purchase #4	$56.53	8.245%	$61.1909	$61.19	$61.20	$61.20
Purchase #5	$11.42	5.434%	$12.0406	$12.04	$12.05	$12.00
Purchase #6	$95.52	5.673%	$100.9388	$100.94	$100.95	$100.90
Purchase #7	$83.86	12.321%	$94.1924	$94.19	$94.20	$94.20
7 purchase totals =	$420.65		$460.0219	$460.02	$460.05	$460.00