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	$120.46	9.405%	$131.7893	$131.79	$131.80	$131.80
Purchase #2	$178.48	6.556%	$190.1811	$190.18	$190.20	$190.20
Purchase #3	$116.38	10.127%	$128.1658	$128.17	$128.15	$128.20
Purchase #4	$180.78	4.468%	$188.8573	$188.86	$188.85	$188.90
Purchase #5	$177.72	6.527%	$189.3198	$189.32	$189.30	$189.30
Purchase #6	$149.75	13.239%	$169.5754	$169.58	$169.60	$169.60
Purchase #7	$99.59	6.150%	$105.7148	$105.71	$105.70	$105.70
7 purchase totals =	$1,023.16		$1,103.6035	$1,103.61	$1,103.60	$1,103.70