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	$69.76	9.566%	$76.4332	$76.43	$76.45	$76.40
Purchase #2	$109.31	12.464%	$122.9344	$122.93	$122.95	$122.90
Purchase #3	$242.25	10.731%	$268.2458	$268.25	$268.25	$268.20
Purchase #4	$195.39	13.786%	$222.3265	$222.33	$222.35	$222.30
Purchase #5	$187.47	4.870%	$196.5998	$196.60	$196.60	$196.60
Purchase #6	$6.95	10.139%	$7.6547	$7.65	$7.65	$7.70
Purchase #7	$215.56	13.455%	$244.5636	$244.56	$244.55	$244.60
7 purchase totals =	$1,026.69		$1,138.7580	$1,138.75	$1,138.80	$1,138.70