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	$102.68	4.134%	$106.9248	$106.92	$106.90	$106.90
Purchase #2	$47.93	13.315%	$54.3119	$54.31	$54.30	$54.30
Purchase #3	$246.95	13.546%	$280.4018	$280.40	$280.40	$280.40
Purchase #4	$209.99	13.745%	$238.8531	$238.85	$238.85	$238.90
Purchase #5	$51.79	4.753%	$54.2516	$54.25	$54.25	$54.30
Purchase #6	$202.50	3.757%	$210.1079	$210.11	$210.10	$210.10
Purchase #7	$149.80	5.778%	$158.4554	$158.46	$158.45	$158.50
7 purchase totals =	$1,011.64		$1,103.3065	$1,103.30	$1,103.25	$1,103.40