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	$77.58	5.829%	$82.1021	$82.10	$82.10	$82.10
Purchase #2	$207.48	10.183%	$228.6077	$228.61	$228.60	$228.60
Purchase #3	$225.67	6.150%	$239.5487	$239.55	$239.55	$239.50
Purchase #4	$52.42	13.415%	$59.4521	$59.45	$59.45	$59.50
Purchase #5	$161.68	11.349%	$180.0291	$180.03	$180.05	$180.00
Purchase #6	$157.92	3.758%	$163.8546	$163.85	$163.85	$163.90
Purchase #7	$54.98	3.462%	$56.8834	$56.88	$56.90	$56.90
7 purchase totals =	$937.73		$1,010.4777	$1,010.47	$1,010.50	$1,010.50