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	$163.98	3.208%	$169.2405	$169.24	$169.25	$169.20
Purchase #2	$173.27	9.159%	$189.1398	$189.14	$189.15	$189.10
Purchase #3	$93.51	3.801%	$97.0643	$97.06	$97.05	$97.10
Purchase #4	$246.50	12.220%	$276.6223	$276.62	$276.60	$276.60
Purchase #5	$151.25	7.321%	$162.323	$162.32	$162.30	$162.30
Purchase #6	$47.78	4.342%	$49.8546	$49.85	$49.85	$49.90
Purchase #7	$189.41	3.686%	$196.3917	$196.39	$196.40	$196.40
7 purchase totals =	$1,065.70		$1,140.6362	$1,140.62	$1,140.60	$1,140.60