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	$245.81	9.703%	$269.6609	$269.66	$269.65	$269.70
Purchase #2	$52.40	4.810%	$54.9204	$54.92	$54.90	$54.90
Purchase #3	$149.27	13.307%	$169.1334	$169.13	$169.15	$169.10
Purchase #4	$111.32	7.741%	$119.9373	$119.94	$119.95	$119.90
Purchase #5	$65.41	10.568%	$72.3225	$72.32	$72.30	$72.30
Purchase #6	$40.93	13.641%	$46.5133	$46.51	$46.50	$46.50
Purchase #7	$64.83	13.480%	$73.5691	$73.57	$73.55	$73.60
7 purchase totals =	$729.97		$806.0569	$806.05	$806.00	$806.00