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	$158.34	8.280%	$171.4506	$171.45	$171.45	$171.50
Purchase #2	$38.29	4.711%	$40.0938	$40.09	$40.10	$40.10
Purchase #3	$26.48	4.179%	$27.5866	$27.59	$27.60	$27.60
Purchase #4	$213.37	8.154%	$230.7682	$230.77	$230.75	$230.80
Purchase #5	$145.59	11.477%	$162.2994	$162.30	$162.30	$162.30
Purchase #6	$178.88	6.389%	$190.3086	$190.31	$190.30	$190.30
Purchase #7	$115.93	3.722%	$120.2449	$120.24	$120.25	$120.20
7 purchase totals =	$876.88		$942.7521	$942.75	$942.75	$942.80