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	$107.77	3.675%	$111.7305	$111.73	$111.75	$111.70
Purchase #2	$38.32	5.113%	$40.2793	$40.28	$40.30	$40.30
Purchase #3	$76.51	13.403%	$86.7646	$86.76	$86.75	$86.80
Purchase #4	$170.80	11.669%	$190.7307	$190.73	$190.75	$190.70
Purchase #5	$156.31	7.189%	$167.5471	$167.55	$167.55	$167.50
Purchase #6	$203.94	9.844%	$224.0159	$224.02	$224.00	$224.00
Purchase #7	$130.74	10.112%	$143.9604	$143.96	$143.95	$144.00
7 purchase totals =	$884.39		$965.0285	$965.03	$965.05	$965.00