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	$240.81	10.510%	$266.1191	$266.12	$266.10	$266.10
Purchase #2	$210.68	6.292%	$223.936	$223.94	$223.95	$223.90
Purchase #3	$82.39	8.412%	$89.3206	$89.32	$89.30	$89.30
Purchase #4	$13.88	10.166%	$15.291	$15.29	$15.30	$15.30
Purchase #5	$163.98	12.544%	$184.5497	$184.55	$184.55	$184.50
Purchase #6	$108.66	13.307%	$123.1194	$123.12	$123.10	$123.10
Purchase #7	$175.41	13.854%	$199.7113	$199.71	$199.70	$199.70
7 purchase totals =	$995.81		$1,102.0471	$1,102.05	$1,102.00	$1,101.90