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	$90.30	7.579%	$97.1438	$97.14	$97.15	$97.10
Purchase #2	$167.78	8.646%	$182.2863	$182.29	$182.30	$182.30
Purchase #3	$72.94	13.566%	$82.835	$82.84	$82.85	$82.80
Purchase #4	$87.76	7.177%	$94.0585	$94.06	$94.05	$94.10
Purchase #5	$57.67	13.452%	$65.4278	$65.43	$65.45	$65.40
Purchase #6	$90.45	9.428%	$98.9776	$98.98	$99.00	$99.00
Purchase #7	$103.82	12.798%	$117.1069	$117.11	$117.10	$117.10
7 purchase totals =	$670.72		$737.8359	$737.85	$737.90	$737.80