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	$190.45	10.219%	$209.9121	$209.91	$209.90	$209.90
Purchase #2	$200.66	8.636%	$217.989	$217.99	$218.00	$218.00
Purchase #3	$107.98	8.583%	$117.2479	$117.25	$117.25	$117.20
Purchase #4	$162.85	9.693%	$178.6351	$178.64	$178.65	$178.60
Purchase #5	$250.96	7.418%	$269.5762	$269.58	$269.60	$269.60
Purchase #6	$177.66	10.357%	$196.0602	$196.06	$196.05	$196.10
Purchase #7	$61.97	6.344%	$65.9014	$65.90	$65.90	$65.90
7 purchase totals =	$1,152.53		$1,255.3219	$1,255.33	$1,255.35	$1,255.30