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	$242.43	11.208%	$269.6016	$269.60	$269.60	$269.60
Purchase #2	$230.33	10.395%	$254.2728	$254.27	$254.25	$254.30
Purchase #3	$207.63	6.115%	$220.3266	$220.33	$220.35	$220.30
Purchase #4	$247.82	13.678%	$281.7168	$281.72	$281.70	$281.70
Purchase #5	$5.82	9.563%	$6.3766	$6.38	$6.40	$6.40
Purchase #6	$59.50	5.551%	$62.8028	$62.80	$62.80	$62.80
Purchase #7	$89.47	12.811%	$100.932	$100.93	$100.95	$100.90
7 purchase totals =	$1,083.00		$1,196.0292	$1,196.03	$1,196.05	$1,196.00