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	$199.64	7.582%	$214.7767	$214.78	$214.80	$214.80
Purchase #2	$123.46	4.226%	$128.6774	$128.68	$128.70	$128.70
Purchase #3	$238.93	13.623%	$271.4794	$271.48	$271.50	$271.50
Purchase #4	$166.97	6.774%	$178.2805	$178.28	$178.30	$178.30
Purchase #5	$162.72	7.300%	$174.5986	$174.60	$174.60	$174.60
Purchase #6	$211.72	5.474%	$223.3096	$223.31	$223.30	$223.30
Purchase #7	$105.99	3.513%	$109.7134	$109.71	$109.70	$109.70
7 purchase totals =	$1,209.43		$1,300.8356	$1,300.84	$1,300.90	$1,300.90