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	$215.85	4.470%	$225.4985	$225.50	$225.50	$225.50
Purchase #2	$172.39	9.311%	$188.4412	$188.44	$188.45	$188.40
Purchase #3	$8.57	4.752%	$8.9772	$8.98	$9.00	$9.00
Purchase #4	$57.62	7.368%	$61.8654	$61.87	$61.85	$61.90
Purchase #5	$72.49	11.494%	$80.822	$80.82	$80.80	$80.80
Purchase #6	$136.83	11.146%	$152.0811	$152.08	$152.10	$152.10
Purchase #7	$116.77	4.360%	$121.8612	$121.86	$121.85	$121.90
7 purchase totals =	$780.52		$839.5466	$839.55	$839.55	$839.60