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	$81.47	12.259%	$91.4574	$91.46	$91.45	$91.50
Purchase #2	$174.50	13.663%	$198.3419	$198.34	$198.35	$198.30
Purchase #3	$133.61	7.457%	$143.5733	$143.57	$143.55	$143.60
Purchase #4	$65.59	9.866%	$72.0611	$72.06	$72.05	$72.10
Purchase #5	$101.93	3.753%	$105.7554	$105.76	$105.75	$105.80
Purchase #6	$180.85	5.541%	$190.8709	$190.87	$190.85	$190.90
Purchase #7	$202.56	4.179%	$211.025	$211.03	$211.05	$211.00
7 purchase totals =	$940.51		$1,013.0850	$1,013.09	$1,013.05	$1,013.20