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	$76.86	9.772%	$84.3708	$84.37	$84.35	$84.40
Purchase #2	$214.30	3.762%	$222.362	$222.36	$222.35	$222.40
Purchase #3	$136.84	6.569%	$145.829	$145.83	$145.85	$145.80
Purchase #4	$103.30	12.817%	$116.54	$116.54	$116.55	$116.50
Purchase #5	$188.54	6.153%	$200.1409	$200.14	$200.15	$200.10
Purchase #6	$138.53	11.600%	$154.5995	$154.60	$154.60	$154.60
Purchase #7	$157.91	11.133%	$175.4901	$175.49	$175.50	$175.50
7 purchase totals =	$1,016.28		$1,099.3323	$1,099.33	$1,099.35	$1,099.30