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	$155.93	5.736%	$164.8741	$164.87	$164.85	$164.90
Purchase #2	$94.81	10.842%	$105.0893	$105.09	$105.10	$105.10
Purchase #3	$125.28	9.397%	$137.0526	$137.05	$137.05	$137.10
Purchase #4	$158.93	8.631%	$172.6472	$172.65	$172.65	$172.60
Purchase #5	$149.37	12.760%	$168.4296	$168.43	$168.45	$168.40
Purchase #6	$175.50	5.649%	$185.414	$185.41	$185.40	$185.40
Purchase #7	$157.48	9.618%	$172.6264	$172.63	$172.65	$172.60
7 purchase totals =	$1,017.30		$1,106.1332	$1,106.13	$1,106.15	$1,106.10