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	$84.26	7.525%	$90.6006	$90.60	$90.60	$90.60
Purchase #2	$222.98	12.840%	$251.6106	$251.61	$251.60	$251.60
Purchase #3	$38.32	13.222%	$43.3867	$43.39	$43.40	$43.40
Purchase #4	$210.74	8.599%	$228.8615	$228.86	$228.85	$228.90
Purchase #5	$211.52	8.564%	$229.6346	$229.63	$229.65	$229.60
Purchase #6	$78.65	4.841%	$82.4574	$82.46	$82.45	$82.50
Purchase #7	$119.46	4.302%	$124.5992	$124.60	$124.60	$124.60
7 purchase totals =	$965.93		$1,051.1506	$1,051.15	$1,051.15	$1,051.20