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	$78.27	10.265%	$86.3044	$86.30	$86.30	$86.30
Purchase #2	$21.34	12.611%	$24.0312	$24.03	$24.05	$24.00
Purchase #3	$212.55	12.402%	$238.9105	$238.91	$238.90	$238.90
Purchase #4	$119.78	6.864%	$128.0017	$128.00	$128.00	$128.00
Purchase #5	$230.76	10.575%	$255.1629	$255.16	$255.15	$255.20
Purchase #6	$129.61	9.666%	$142.1381	$142.14	$142.15	$142.10
Purchase #7	$169.49	11.607%	$189.1627	$189.16	$189.15	$189.20
7 purchase totals =	$961.80		$1,063.7115	$1,063.70	$1,063.70	$1,063.70