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	$222.67	10.638%	$246.3576	$246.36	$246.35	$246.40
Purchase #2	$221.90	12.419%	$249.4578	$249.46	$249.45	$249.50
Purchase #3	$100.94	13.646%	$114.7143	$114.71	$114.70	$114.70
Purchase #4	$89.67	10.777%	$99.3337	$99.33	$99.35	$99.30
Purchase #5	$48.75	13.842%	$55.498	$55.50	$55.50	$55.50
Purchase #6	$99.66	8.604%	$108.2347	$108.23	$108.25	$108.20
Purchase #7	$142.85	9.102%	$155.8522	$155.85	$155.85	$155.90
7 purchase totals =	$926.44		$1,029.4483	$1,029.44	$1,029.45	$1,029.50