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	$163.56	8.854%	$178.0416	$178.04	$178.05	$178.00
Purchase #2	$85.40	5.176%	$89.8203	$89.82	$89.80	$89.80
Purchase #3	$55.25	4.265%	$57.6064	$57.61	$57.60	$57.60
Purchase #4	$203.57	13.782%	$231.626	$231.63	$231.65	$231.60
Purchase #5	$117.73	11.228%	$130.9487	$130.95	$130.95	$130.90
Purchase #6	$214.67	6.743%	$229.1452	$229.15	$229.15	$229.10
Purchase #7	$133.83	5.717%	$141.4811	$141.48	$141.50	$141.50
7 purchase totals =	$974.01		$1,058.6693	$1,058.68	$1,058.70	$1,058.50