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	$246.45	13.839%	$280.5562	$280.56	$280.55	$280.60
Purchase #2	$7.35	5.435%	$7.7495	$7.75	$7.75	$7.70
Purchase #3	$220.99	5.720%	$233.6306	$233.63	$233.65	$233.60
Purchase #4	$191.59	10.421%	$211.5556	$211.56	$211.55	$211.60
Purchase #5	$6.95	10.109%	$7.6526	$7.65	$7.65	$7.70
Purchase #6	$92.93	12.627%	$104.6643	$104.66	$104.65	$104.70
Purchase #7	$196.47	4.154%	$204.6314	$204.63	$204.65	$204.60
7 purchase totals =	$962.73		$1,050.4402	$1,050.44	$1,050.45	$1,050.50