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	$80.46	3.720%	$83.4531	$83.45	$83.45	$83.50
Purchase #2	$89.89	5.560%	$94.8879	$94.89	$94.90	$94.90
Purchase #3	$23.68	5.434%	$24.9668	$24.97	$24.95	$25.00
Purchase #4	$223.97	7.546%	$240.8708	$240.87	$240.85	$240.90
Purchase #5	$164.72	8.607%	$178.8975	$178.90	$178.90	$178.90
Purchase #6	$197.80	7.136%	$211.915	$211.92	$211.90	$211.90
Purchase #7	$242.72	11.675%	$271.0576	$271.06	$271.05	$271.10
7 purchase totals =	$1,023.24		$1,106.0487	$1,106.06	$1,106.00	$1,106.20