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	$144.50	4.214%	$150.5892	$150.59	$150.60	$150.60
Purchase #2	$67.55	13.664%	$76.78	$76.78	$76.80	$76.80
Purchase #3	$198.98	7.604%	$214.1104	$214.11	$214.10	$214.10
Purchase #4	$196.60	4.292%	$205.0381	$205.04	$205.05	$205.00
Purchase #5	$96.50	13.336%	$109.3692	$109.37	$109.35	$109.40
Purchase #6	$49.70	13.314%	$56.3171	$56.32	$56.30	$56.30
Purchase #7	$179.98	6.716%	$192.0675	$192.07	$192.05	$192.10
7 purchase totals =	$933.81		$1,004.2715	$1,004.28	$1,004.25	$1,004.30