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	$92.38	3.355%	$95.4793	$95.48	$95.50	$95.50
Purchase #2	$243.70	10.575%	$269.4713	$269.47	$269.45	$269.50
Purchase #3	$145.46	6.646%	$155.1273	$155.13	$155.15	$155.10
Purchase #4	$209.80	9.510%	$229.752	$229.75	$229.75	$229.80
Purchase #5	$138.81	12.687%	$156.4208	$156.42	$156.40	$156.40
Purchase #6	$249.83	12.330%	$280.634	$280.63	$280.65	$280.60
Purchase #7	$46.25	9.303%	$50.5526	$50.55	$50.55	$50.60
7 purchase totals =	$1,126.23		$1,237.4373	$1,237.43	$1,237.45	$1,237.50