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	$192.79	11.580%	$215.1151	$215.12	$215.10	$215.10
Purchase #2	$231.43	5.204%	$243.4736	$243.47	$243.45	$243.50
Purchase #3	$87.38	13.611%	$99.2733	$99.27	$99.25	$99.30
Purchase #4	$115.64	8.402%	$125.3561	$125.36	$125.35	$125.40
Purchase #5	$95.86	4.802%	$100.4632	$100.46	$100.45	$100.50
Purchase #6	$154.27	9.838%	$169.4471	$169.45	$169.45	$169.40
Purchase #7	$20.76	3.826%	$21.5543	$21.55	$21.55	$21.60
7 purchase totals =	$898.13		$974.6827	$974.68	$974.60	$974.80