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	$149.70	13.488%	$169.8915	$169.89	$169.90	$169.90
Purchase #2	$221.50	7.615%	$238.3672	$238.37	$238.35	$238.40
Purchase #3	$210.78	6.674%	$224.8475	$224.85	$224.85	$224.80
Purchase #4	$150.25	12.208%	$168.5925	$168.59	$168.60	$168.60
Purchase #5	$158.99	5.501%	$167.736	$167.74	$167.75	$167.70
Purchase #6	$27.40	6.404%	$29.1547	$29.15	$29.15	$29.20
Purchase #7	$16.63	7.415%	$17.8631	$17.86	$17.85	$17.90
7 purchase totals =	$935.25		$1,016.4525	$1,016.45	$1,016.45	$1,016.50