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	$70.48	9.112%	$76.9021	$76.90	$76.90	$76.90
Purchase #2	$180.65	5.125%	$189.9083	$189.91	$189.90	$189.90
Purchase #3	$43.91	6.727%	$46.8638	$46.86	$46.85	$46.90
Purchase #4	$162.72	10.510%	$179.8219	$179.82	$179.80	$179.80
Purchase #5	$201.77	10.737%	$223.434	$223.43	$223.45	$223.40
Purchase #6	$163.55	10.841%	$181.2805	$181.28	$181.30	$181.30
Purchase #7	$114.28	11.727%	$127.6816	$127.68	$127.70	$127.70
7 purchase totals =	$937.36		$1,025.8922	$1,025.88	$1,025.90	$1,025.90